To resolve the connectivity issue between your iPad and the Roon Server, perform the following steps:
Account Verification: Ensure the Roon Remote app on your iPad is logged into the exact same Roon account as your Roon Server.
Local Network Permission: Open the iOS Settings app on your iPad, scroll down and select the Roon app, then toggle the Local Network permission off and back on.
Attempt to connect the iPad to the Roon Server again after completing these steps.