Moving multisite wordpress to new host (same domains), issues

Hello,

I purchased a multisite wordpress website:
stack52.com
strength.stack52.com
hiit.stack52.com
weightloss.stack52.com

I backed up cpanel using the backup wizard. I uploaded the backup to my new host, and they unpacked it and replaced the previous “empty” cpanel.

I then changed all the name servers in my domains to the new hosts name servers.

Some of the pages will load, but some will not.
These load:
stack52.com
strength.stack52.com

weightloss.stack52.com gives this error “https://weightloss.stack52.com/” but the favicon works! ??

Many of the pages in strength.stack52.com also give that error. The previous owner rebuilt his site and has a lot of 301 redirects. Many of the pages with redirects are broken (but some work).

When I try to log into strength.stack52.com/wp-admin,
I get the following error:

“Error establishing a database connection
This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at localhost. This could mean your host’s database server is down.”

The support at my new host tells me:
“If you run the search and replace for the server name the domains stayed the same but the connections are still pointed to the old server.”

They directed me here for help.

I would deeply appreciate any help.
Thank you,

Kurt