Is there a glue to use?

Depending on what the o-ring is made of the use of glue could cause it to disintegrate. If you are just wanting a seal, silicone grease works well.

The o ring is rubber and the pipe is metal. Silocone adhesive did not work. Thanks for helping.

Could you tell us more about what you are doing?

Not silicon adhesive, silicone plumbing grease. Available at hardware stores.