Timeout period elapsed prior to obtaining a connection from the pool - Azure Flexible MySQL

[Jess Pomfret]

The MySQL instance was automigrated from a single server to a flexible server this morning.

The .NET client was updated from 8.0.21 to 9.0.0 as we were hitting errors that we couldn't connect, which made sense since flexible server required at least 8.0.32.

Since then we found that active connections were increasing close to 300 (which is what we have max_connections set to). We then found wait_timeout has changed from single (120 seconds we think) to 8 hours. We set this value to 120 on the new flexible server. Connections then levelled out - and are around 60-70.

However, we are still getting the following error:

An Exception Occurs In AuthenticateController.ObtainToken.
Exception Thrown: Exception: MySql.Data.MySqlClient.MySqlException (0x80004005): error connecting: Timeout expired.
The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

Any ideas? Or places to look for troubleshooting?