I have eight albums. The index page shows six and the navigation bar at the top indicates there is a second page but when I click on '2' or 'next' I get:
Zenphoto Error: the requested object was not found.
Page: index/2

BUT if I go to the album management page and select either of the two albums that are not shown on the first index page and then use the 'View gallery' button I can get to page 2 and see both of the albums, i.e. index/2 does exist.

Why can't the navigation on page one find page 2?

Possibly you have modrewrite enabled which the backend does not use and either the server does not support it (which would be quite strange these days) or the htaccess file is not in place or not correct (itshould have "htaccess file version 1.4.12" on top).
Depending where you installed check the rewritebase. If should be a slash if installed in a domain root or a folder if in a sub folder.

Assuming you are on an Apache server. Other servers like Nginx etc. may require extra setup.

So first try to disable modrewrite on Options > General to see if that works.

As requested, I have disabled modrewrite but I still get the same error. I've also noticed the behaviour is inconsistent. I'm using the Zenpage theme by the way.

If I start from https://[myDomain]/imageGallery/index.php then the page is headed with a banner that says 'Gallery' and under that there is a bar showing the beginnings of a breadcrumb trail, it just says 'Home'. The main area has 'prev 1 2 next' at the top. If I click on '2' or 'next, I get the error. If I go back by clicking on 'Home' the error will reoccur if I try again.

BUT if I go back from the error page by clicking on 'Gallery', the URLof the home page becomes https://[myDomain]/imageGallery/index.php?p=gallery and the breadcrumb trail says 'Home >> Gallery' and now clicking on '2' or 'next' works as expected.

Does this give any clues to the root of the problem?

So, no further insight into this behaviour?

Meanwhile, I have worked around the problem by increasing the number of albums shown on the gallery home page from the default of six to nine (via Options | Theme).

Sorry, yesterday I tried to answer but the forum/server hang a little and then I forgot/had no time to re-post:

I have no idea what may be wrong currently. You should see a url like `index.php?page=2` or `p=gallery&page=2` without modrewrite. I assume you are on the latest Zenphoto btw. Without modrewrite URLs should work. I admit we focus on the modrewrite links so I just tried on a test install and it work as intended for me.

Outdated browser cache may interfere though and cause all sorts of sideeffects, so be sure to force clear that after switching the option.

Gallery and home are generally synonyms as "gallery" traditionally means "site" in general from times when Zenphoto was just a gallery and "home" was always the gallery meaing toplevel albums. Some themes also use a gallery page as they may allow to set a Zenpage page as the home page. Currently the gallery page is not the home and doubles the home page if that is also the gallery (metadata if you enabled the html_meta_data plugin should place a canicallink element to help here). This is not optimal but is on the long list…

OK, I too couldn't reach this forum for a while yesterday.

As I said above, I unticked 'modrewrite' as soon as you suggested that but it made no difference at that time, the problem persisted so I worked around the by increasing the number of thumbnails per page from 6 to 9, so that there would only be one page.

Having read your latest post wanted to check how the URLs were shown when I had multiple pages so I reduced the number of thumbnails from per page from 9 down to 4.

Having done that, I'm pleased to report that now, the error does *not* occur. The 'prev 1 2 next' navigation is working as expected now. Hurrah! Your suggestion of an outdated browser cache seems like the explanation as to why disabling modrewrite didn't help when I first made that change.

Thank you for your patience with me.

Great it works finally as it was really not usual behaviour. Browser caches are some times very persistent these days and frequenty cause unexpected side effects sadly.

Still wondering why your might have a server that does not support modrewrite. Did you check if the htaccess file is there? Zenphoto tries to check on setup if modrewrite is available but that check is sadly not 100% reliable.

Sorry for the slow response...

The Admin Overview Installation Info panel for my set up reports:
Zenphoto version 1.6.8
Locale setting has failed
Server path:[redacted]/imageGallery
WEB path: /imageGallery
PHP Session path: /var/lib/php/sessions
Current gallery theme: Zenpage
Server software: Apache/2.4.68 (Debian)
PHP version: 8.4.24
Graphics support: PHP GD library 2.3.3
supporting: gif, jpg, jpeg, png, wbmp, webp, avif
PHP memory limit: 128M (Note: Your server might allocate less!)
Database: MariaDB 11.8.6
Database handler: mysqli
Database client: mysqlnd 8.4.24
Database name: [redacted]
Database table prefix: zp_
Spam filter: No spam filter configured
CAPTCHA generator:

ZP setup explicit reports it can't find a working modrewrite. Asking my hosting company about modrewrite is on my To Do list, but it's low priority as having ZP work by unticking that option is OK for me.

There is a .htacces file in the /imageGallery folder. It's contents are:

# htaccess file version 1.4.12;
# Rewrite rules are now handled by PHP code
# See the file "zenphoto-rewrite.txt" for the actual rules
#
# These rules redirect everything not directly accessing a file to the Zenphoto index.php script
#
<IfModule mod_autoindex.c>
IndexIgnore *
</IfModule>
<IfModule mod_rewrite.c>
RewriteEngine On

RewriteBase /imageGallery/

RewriteCond %{REQUEST_URI} !(/$|\.)
RewriteRule (.*) %{REQUEST_URI}/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [L]

RewriteRule ^.*/?$ index.php [L,QSA]

</IfModule>

That all looks good.