Your LN channel might be no remaining funds or offline.

I tried to find the solution about your issue in google and I found two possible sources of solutions to take your bitcoin out from the lightning network.

I don't know if this will work as I just search it from google.

Check these two links below.

- https://lightning-wallet.com/recovering-lost-balance#recovering-lost-balance
- https://lightning-wallet.com/reimbursing-funds-locked-in-a-lost-payment-channel#reimbursing-funds-locked-in-a-lost-payment-channel