After a week of uplift on a trailer my Shimano XT front brake has died, zero power in it. Exactly the same thing happened last year after a week. Bleeding has no effect. Anyone else had this issue, rear brake is fine.

lever feel?  Firm or back to bars?

How much brake pad material is left?

Are the pistons moving freely?

If the trailer caused it, it’s a bleeding issue. If it’s not a bleeding issue, the trailer didn’t cause it (unless the trailer ripped a hose).

Even more likely if it’s the front and not the rear playing up as the front caliper is lifted higher than the lever.

How is the lever feel? If it has a solid lever feel, then it’s not air in the system so bleeding won’t help?

How are the pads? Are they glazed, badly worn, or oily? New pads should fix the first two. If they’re oily, you have leaky seals.