UR28M jack stuck

Years ago I bought a UR28M that I have not yet uset. Decided to test it today. Pluged in my guitar and did some recodring.
Now trouble is. The Jack is simply stuck in LINE 1. I do not want to use too much power incase I destroy something, and I dont want to risk that the first day of use. But I dont want to be stuck with the jack in there forever either. Anyone here technically enough to know if there is a way to release a stuck Jack plug? (My cable has been working fine and I think it must be something in the jack):