Prestashop database expert needed

I have a website that my developer has moved to a new domain name with a new SSL certificate. There are problems with connection, the database will not connect to the new domain. My developer thinks it is a problem with permissions but cannot solve it. My developer has said:

The php version has to be the same as it is on the same account – I think they were thinking this had been transferred from another host.
I’ve tried changing permissions – this led to a slightly different error message, which does at least confirm everything is there, just not connecting properly.

we need a specialist in prestashop databases. I daren’t just meddle with the code, and I’ve never worked directly on databases. I don’t think it will be difficult for someone who works in this area, so maybe a post on PPH would find someone suitable? I’d be happy to liaise and explain what’s been done so far.