Upgrade from 16 to 18 broke system

Installing my Dolibarr
1

I ran the install /upgrade stage by stage, and ended up with a white screen.
Now all I get is database access errors.
Message: host=localhost, port=3306, user=dolibarrdebian, databasename=dolibarrdebian, Failed to connect

Unable to reinstall 16 on spare system as php 7 no longer available.
Unable to import database as instructions say to use same version as old system (bad)

Any suggestions please

2

have you tried connecting to the database outside Dolibarr using exactly the same methods?

3

Yes using MySQL Workbench. BUT with different user name, which has limited rights

4

try with the same user