All lightning seeds have reserve limits for potential channel closes (regardless if you have a channel open)

You will not be able to send funds out, unless;
- you enter the CLI and edit those limits 

It's easier to just import that seed into another wallet and sweep funds from there
- best is Sparrow wallet, which allows to you see all depths/accounts the view your change addresses


This is a known and large problem imo and it has yet to be fixed. Many devs refuse to acknowledge this is a problem and will not "fix" it.


Best of luck to you