Perhaps there is an issue with your iPad's settings.
Start by resetting the settings and preferences on your iPad:
Settings > General > Reset > Reset All Settings
The data on the iPad is not affected, but you will have to enter your favorite settings and preferences again, including the password for your Wi-Fi router.
Next you may also want to reset the network settings and other settings.
If any of this works, make a backup of your iPad immediately.
These settings are also backed up in a backup.
Restoring from a faulty backup would therefore also restore the faulty settings.
If all of this does not help, start a new discussion to reach other iPad users with better ideas.