Have you tried disconnecting and then reconnecting the iPad’s Wi-Fi connection? If this doesn’t work for you, try deleting and reinstalling the Roon app.
I’m sorry we’ve been so late to reply to your post . I had hoped it would be much much sooner.
I appreciate you trying out @Martin_Webster’s suggestion (thanks, @Martin_Webster!). As a second first troubleshooting step, could you please check the iOS permissions on your iPad and iPhone?