Ipad not getting messages from iPhone. iMessage button is on

Welcome to the Apple Support Communities!

I understand you are receiving messages on your iPhone, but not on your iPad. The resource below will provide some settings that you may need to adjust on your devices. I've highlighted some key information here for you. Click on the link for complete details.
If you can‘t send or receive messages on your iPhone, iPad, or iPod touch
If you receive messages on one device but not the other:

If you have an iPhone and another iOS device, like an iPad, your iMessage settings might be set to receive and start messages from your Apple ID instead of your phone number. To see if your phone number is set to send and receive messages, go to Settings > Messages, and tap Send & Receive.

If you don't see your phone number, you can link your iPhone number to your Apple ID so you can send and receive iMessages from your phone number. You can also set up Text Message Forwarding so you can send and receive MMS and SMS messages on all of your Apple devices.

Take care.