Upgrading Drupal

So, long story short;

1. Decided to upgrade Drupal version - I was on latest Drupal 8 trying to upgrade latest D9.

2a. Manually back up. 2b. Used Softaculous, backed up, then upgrade.

3. Upgrade done, site works at first, but errors when I try to log in or access update.php.

4. No problem! I got backups!  Use softaculous backup to revert.

5. Site did not go back to its original form, shows installation page. 

6. OK, a bit concerning, no problem! I got manual backup! Manually revert.

7. Site still shows installation page.

Hi All,

I have had Drupal running for about 10 years and upgraded many times. I know Drupal was first made for Linux and slowly became adapted to windows.  A lot has improved with windows running php.

A couple of weeks ago I updated php to 8.1.1 and have had a time with several issues and have been unable to google any good information I need.

After the two weeks I have everything running with no errors.

After an Update from Drupal 8 to Drupal 9. Most parts of the site run, but my main problem at the moment is that I can't login. If I do so, the page refreshes but shows no error. I have looked into the log files, but I can't find anything strange.

I have done a few things:

- cleared cache
- deactivated https redirection

After an internet research, I found similar Problems in connection with the redirect_after_login module. But I don't have installed this module.

Where could I look next to find a solution?

Thanks for your help,
Chris

I see a lot of articles on drupal.org talking about various aspects of upgrading D7 to D8 or D9 - how to prepare, checking compatibility, possible issues, etc. Several say going directly to D9 is fine, but far more talk about going to D8 first.

What I have not found yet - they are probably in plain site, but I'm not seeing them - are the two articles that list the actual procedures for upgrading D7 to D8 and D9, respectively.

Can anyone provide those links, please?

I have just updated my site from 8.9.20 to 9.3.2 using composer. Everything seems OK except that two views database updates caused a failure, even after cache rebuild:

views module

• Add the identifier option to all sort handler configurations.
• Rebuild routes to fix view title translations.

This was the fail message:

In block layout, the place block buttons have stopped working. the loading icon appears next to the button after clicking for a moment and then nothing happens. I can right-click them and open them in a new tab, but there is no longer a popup like there used to be. I thought it had something to do with an error I was getting in regards to a custom block. After fixing it, the place button issue still exists. It's such a strange error I'm unsure where to go next to troubleshoot the issue. any recommendations? 

Thank you for the suggestions.