My apple pencil 1st gen is not pairing with my ipad 8th gen after 4 months use.been turning on and off and hard resetting the ipad, but still it wont pair. My bluetooth cannot find my apple pencil even it is already plugged in.

Something maybe wrong with your Pencil and/or iPad.

You need to search online for your nearest, “local” Apple store location and call contact phone numbers and call to make an appointment to have both your Apple iPad and Pencil diagnosed and options presented you.

Failing that,

You need to contact Apple support via the contact support link located at the upper right hand corner of every Webpage of these Apple support communities.

Use the Hardware Repair & Device Performance and Connectivity support categories.

OR

by installing and using the Apple Support app found in the iOS App Store.

Tap the iOS App Store link below.

https://apps.apple.com/us/app/apple-support/id1130498044

OR

Call contact Apple via the support numbers found in the link bekow.

Contact - How to Contact Us - Apple

Tap the link below.

https://www.apple.com/contact/

Best of Luck to You!