I just upgraded to 1.5.9 (followed the instructions to the T). I went to my main page to run setup, but it was blank. Even navigating to the "www.yoursite.org/zenphoto/zp-core/setup.php" yielded a blank page. The file is there, permissions as they should be. No idea what's going on.

PHP Version is 7.4.20.

Please review the debug log and your server php error log.

Debug Log:

{23658:Wed, 10 Nov 2021 16:17:00 GMT}
  WARNING: mysqli::query(): (HY000/3685): Illegal argument to a regular expression. in /home/dh_k84i36/mydomain.net/gallery/zp-core/functions-db-MySQLi.php on line 84 
mysqli->query called from query (functions-db-MySQLi.php [84]) from query_full_array (functions-db-MySQLi.php [130])
from SearchEngine->searchFieldsAndTags (class-search.php [1081])
from SearchEngine->getSearchImages (class-search.php [1544])
from SearchEngine->getImages (class-search.php [1626])
from SearchEngine->getNumImages (class-search.php [1509])
from getNumImages (template-functions.php [2097])
from include (search.php [9])
from include (index.php [130])
from index.php [56]

{6104:Wed, 10 Nov 2021 19:35:39 GMT}
  EXCEPTION (0): syntax error, unexpected '

We'll try to give simple answers when possible ;-)

The lines your logs reference seem to indicate a problem with the mysql database configuration or credentials you entered.

Please check the credentials you got from your webhost and check if you have them defined correctly in zp-data/zenphoto.cfg.php.

Thanks, I really appreciate that

I checked my credentials in the file, all looks normal. My webhost updated their PHP version about a month ago, but my gallery was running on it just fine.

I just noticed something strange going on in my phpMyAdmin (my databases not showing up in the list, which has happened once before) and I've contacted my webhost about it. But I could see the databases when I was trying to troubleshoot this problem yesterday, so I really have no idea what the issue might truly be here.

I am sorry, PHP 7.4.20 should work (8 does not yet). But if the databases / the database server were gone temporarily that could explain such issues. Guess we'll have to see what the host says…

I haven't heard back from my host yet, but the PHP upgrade was indeed to 8. (Uh oh.) This was about mid-October. However, I ran a PHP version check on my site just yesterday (and I tested it just now), and it still says 7.4.20. I think I may install the previous ZenPhoto version just to get my gallery up and running again. Once I can see my databases again, of course. Thank you very much for your help thus far.

Ok, let us know if you find out anything.

Nothing wrong with my host; the databases appeared again after a few minutes.

I just tried installing 1.5.7 (after a failed attempt to install 1.5.8), which I think was the last working version I had before I tried to upgrade, but it yielded the same problem with the blank pages (as it did with 1.5.8). The debug log reads this same error several times:

{13770:Thu, 11 Nov 2021 14:39:12 GMT}
EXCEPTION (0): syntax error, unexpected '

I see indeed two possibilites right now: Either something is not right on the configuration on your host somehow. Or something went wrong uploading the files.

If you don't want to loose your data, don't change the database and don't delete/overwrite the albums folder. Actually you just need to follow the upgrade instructions on our site. https://www.zenphoto.org/news/installation-and-upgrading

After tinkering around with the upgrade for some time with no success, I went ahead and just emptied my database and tried to do a clean install of 1.5.7, the last version I was successfully using before I tried upgrading.

Now I'm getting a message on the setup page during the install process that says "We do not test upgrades that skip releases. We recommend you upgrade in sequence."

I don't understand how I could be getting an upgrade error when attempting a totally clean install. I didn't run across this problem the last time I was first installing 1.5.7.

In any case, the install is hung up and I cannot proceed. Advice?

The message is correct since you skipped 1.5.8. There should not be much difference with 1.5.9 actually. I did the upgrade on several standard shared hosts without any problem. All I again can request is the usual "please review the error logs". Meaing ZP's own debuglog and the setuplog and if you can your server's errorlog. Otherwise we are guessing around. If you have any third party themes or plugins remove them for now just in case.