[Koha] Upgrade problem Debian Packages

[clint.deckard]

Following an upgrade form 16.05 to 17.11 using the packages (and 
koha-restore) on Debian Jessie I get the following error when trying to 
access the staff or opac interface;
"DBIx::Class::Storage::DBI::catch {...} (): DBI Connection failed: 
Access denied for user 'koha_instance'@'localhost' (using password: YES) 
at /usr/share/perl5/DBIx/Class/Storage/DBI.pm line 1490. at 
/usr/share/koha/lib/Koha/Database.pm line 100"

I did notice the error during koha-restore 'DROP USER koha_instance 
failed' (approx).

I'd appreciate some help.

Clint.