New iPad Bluetooth doesn’t pair with headphones, previous iPad connected just fine.

See:

• Set up and use Bluetooth accessories on iPad - Apple Support
• If you can't connect a Bluetooth accessory to your iPhone, iPad, or iPod touch - Apple Support

be sure that the old one do not have an active connection with the headphones at the time

be sure you put the headphones into pairing mode this is require the first time one connect a headset with a new device

how one goes about putting the headset into pairing/discovery mode differ from headset to headset it should be in the manual of the headset and on the website of the manufacturer

Dale93 Said:

"New iPad Bluetooth doesn’t pair with headphones, previous iPad connected just fine. New iPad won’t pair with my headphones, old iPad did."

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Incompatibility being the Culprit:

Look at the original packaging of the headphones. It would say what iPad model and iPadOS it is compatible with.