after updating my two iPad Pro (11 and 12) to the latest 17.5.1 update I've lost ability to add/purchase any data plans, the option 'Find New Plan' remains greyed out no matter what I try: network settings reset, reboot, soft reset (valume up, down, and power), power cycling - nothing helps. the only other available options are 'Transfer iPad Plan', 'Join iPhone Plan' and 'use QR code'.
It is perhaps curious that your two iPads have a similar problem - as there are no widespread reports of the issue that you describe. Were your iPads purchased from a Cellular Carrier - or directly from Apple? Devices purchased from a Cellular Carrier can sometimes be subsidy-locked by the Carrier, or have their eSIM disabled.
Do you have a physical DataSIM installed? If yes, try removing and reinstalling the SIM - or remove the SIM altogether.
If you are experiencing issues after updating your iPad to a more recent version of iPadOS, a forced-restart of your iPad - as this will often clear an isolated software issue:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
If the problem with adding Cellular Data Plans persists after performing the restart, check for a Carrier Update. If available, these are offered when you access the "About" page in iPad settings:
Settings > General > About
If an available update is listed, apply the update - and then restart your iPad. If a Carrier Settings update is not available, try resetting your iPad's Network Settings:
Settings > General > Transfer or Reset iPad > Reset > Reset Network Settings
Otherwise, it may be necessary to fully reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:
How to back up your iPhone, iPad, and iPod touch - Apple Support
When you are happy to proceed, you can perform the reset from iPad settings:
Settings > General > Transfer or Reset iPad > Reset > Reset All Settings
If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
Should the problem remain unresolved, you would be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad - and you can explore your available options:
17.5.1 udpate screwed up my data plan options
