Hi Sean,
You should only need to reconfigure PAW if you install a new microSD card. The best way to update these days (especially if you have complex settings) is to use the PilotAware Firmware Updater App - available via the Apple App Store, or for Android devices, the Google Play Store. This updates PAW without having to remove it from the aircraft - or even opening the case, and without changing any of its previous configuration. It is generally also much quicker.
In your case, as you say you swapped to a new card, you will have to reconfigure the relevant USB port in PAW Configure to get your ADSB working again. (probably Port 2 - which is the lower one in the left hand row with the Ethernet port to its left - it should normally have a clear USB plug in it). The relevant port needs to be configured to ‘Transponder Trig’ and ‘9,600 Baud’ (providing your transponder is also configured to the recommended 9,600 Baud Rate - they must both be set to the same Baud Rate (speed)). Don’t forget to Save the PAW Configure settings once you have changed them. If you’re not sure how to check the Trig settings, it’s best to dig out the operating instructions (available for download online) and check how to do this properly, as although it’s easy to get into settings mode, you can easily muck up the unit settings once there if you don’t follow the instructions carefully.
Re the White Screen on the separate phone you are using as a permanent Radar Screen, this sounds like a setting on the phone, but difficult to diagnose without more information - for a start, what make / model of phone, and are you talking about PAW or SkyDemon Radar?
Best Regards
Peter