Any attempted page edit leads to login screen

[nturner]

Serially from 2.8.3 SP6 via 10

[dbs]

From which WB version you have upgraded?

[nturner]

Same problem on sister site edren.org not fixed by reversion to PHP 5.6 

[nturner]

That helps! The problem appears to be fixed by going back down to PHP5.6
7.0 or 7.1 break it.
I didn't try reloading 2.11 so far

[dbs]

Hello, which PHP version you use? At least 5.6.
It is possible that not all files were transferred during the upload. Please repeat this process. Load up all WB 2.11 files again.

[nturner]

Since 2.11, any attempt to edit a page leads to being shown login screen. Not logged out,
Testing browsers, in Safari sometimes get error show_menu2 error: $aOptions is invalid. No flags supplied!
OR {"content":[],"message":"Access denied","success":false}
Removing all menu calls from template doesn't fix it.

Any ideas please??