OK, I’ve made many tests and here is what I found in MY SCENARIO.
Over the years, I have gotten into the habit of changing WP prefixes for database and tables.
I believe that all my standing multi-sites were so customized.
The host did a fresh upgrade to their server sides but Softaculous would still produce broken multi-sites (with add-ons and prefixes moded).
So I just did straight forward installs of new multi-sites without add-ons, without changing prefixes Nothing except ticking the multi-site on and I created 2 working multi-sites.
My recommendation is that WP either inform users that changing prefixes is no longer a security enhancement option or to fix this issue in future updates so that we can add the prefix customization option as well as other add-on options to the install of a multi-site.
Hope this helps.
Sorry guys, I thought two tests would be enough and sure enough the third time I tried it broke again!
This seems an inconsistent issue at least for my situation.
Hit and miss!
I have contacted my host to see if the techs can test and put their brains to work on this one…..
I did it again and remembered that I needed to use a “normal” username.
The latest install that didn’t work had a hardened username (I previously said not to use one).
So this time, it worked.
I’d like to know what others experience who share some of the conditions I have described above in my posts and does my final resolution work in your case?