Login dialogue interrupts admin changes - cannot set up site

I am a long-time user of ZenCart and have never had any problems with installation. It has always worked, until now!
I recently had a site configuration upgrade (PhP upgrade) and had some external developers upgrade their own system. As a result the 1.5.3 store got broke.
So I have tried to start a new 1.5.7 installation. https://www.ausi.com.au/zen2020
Along the way I have deleted all previous installs.

• I am trying to start anew.
• No plugins yet.
• My current install is FTP upload and running ZC_Install.
• PHP is 7.1
• MySQL is 5.6.47

The problem is everything works as normal, I can login as admin, but as soon as I navigate away from ANY screen, or save changes, I am returned to the login dialogue and no changes are saved.

I have tried the installatron version, I have done the manual install. I get the same result. I deleted all earlier version databases in case that was causing a problem. Nothing makes any difference. In response to another thread, I tried rebooting my computer. No difference. Same on any other device.

My hosting platform (C-Panel) can only suggest upgrading the PhP (currently 7.1 to 7.4) but this would break my main user administration system. If this would fix the problem I can create a subdomain for the store.

Many thanks

The scenario of the Admin logging itself out after any action, especially after doing an upgrade on the same domain, is typically representative of having old cookies in the browser cache.
Clearing the browser's cache/cookies usually resolves that.
This can also usually be confirmed by testing the Admin functionality from another computer that's never used your Admin before (or in Private Browsing/Incognito mode in the browser): if it works there then the problem is isolated the to other browser.

Related:
https://docs.zen-cart.com/user/troubleshooting/cant_login/
https://docs.zen-cart.com/user/troubleshooting/cant_stay_logged_in/

Thanks.
I did see that in the various threads, so I have tested that. I have cleared caches and cookies, I have tried new browsers, and I have tried new browsers on new devices (tried on another android tablet).

None of this makes any difference.

Any other ideas?

OK, you gave me some reading... I guess I should read it first and try that!

I have worked through the linked information sheets to no avail.
I have done everything listed and nothing makes a difference.

I have moved the shop to a new subdomain and done an entirely new install. Now at shop.ausi.com.au
No difference. Still can't stay logged in.

Any new ideas?

:smile:
SOLVED::
I changed the PhP for the site to 7.4 instead of 7.1 and the problem was solved.

I conclude that ZC 1.5.7 does not like PhP 7.1 for admin. Maybe this should be added to the support?

This breaks my other database but that is a separate issue.

It's likely that your server's PHP 7.1 configuration has different session settings that are evidently broken. Not uncommon if the server's "primary" version is 7.4 (eg: newer than 7.1) and 7.1 was "added back to the server" to allow for downgrading convenience. Some hosting companies mistakenly fail to ensure the configurations are consistent across versions especially when changing or adding multiple otherwise-incompatible versions on the same server.

Thanks for your thoughts about the docs; yet I see no reason to add anything to the documentation in regard to 7.4 vs 7.1 vs v157 as I've seen no pattern of this situation outside of your setup.

You should backup the /admin/.htaccess file (try renaming it to htaccess_bak) and then check whether the site behavior has changed. If it is so, then you need to co-operate with your hosting to find the correct way to use the supplied .htaccess security guard on your website.