Connection failed to mysql database after upgrade to version 8 AWS RDS

I am experiencing an issue after the MYSQL upgrade from version 5.7 to 8 on AWS RDS. Before the upgrade, my server used to work properly but immediately after getting the database updated to version 8, it appears to be broken. The error is as follows:

Connections could not be acquired from the underlying database!

I am fairly new to MYSQL and I could not find a suitable online solution to solve this issue. Ideally, I would like to know if there is a proper way to view an "in-depth" log about any exceptions causing this as it is the only error message I am getting. Or perhaps, I am looking for some guidance about what might cause this failure in the database connection, please.

I am lost at this point.

Your help will be much more appreciated!

I wish to thank you in advance for your help.