Restore Backup and database backup to a new container to test upgrade

Hi I have taken a backup from SuiteCRM 8.7 and the associated database backup and built a docker container with the database and site restored from the backup.
the database is working and the suitecrem user can access it on the localhost.
but when I try to access the SuiteCRM site I get there message
Composer autoloader not found. please run “composer install”
when I do that and check the permissions on everything, then try again aI get the same message.

I want to test the upgrade to 8.8 on the Docker version before I run the upgrade on the main site (in Digitalocean)

Thoughts anyone.
Thanks

Paul

Is your web root pointed correctly to “public”?

Did your backup bring over the entire contents of the vendor directory?