I contributed $2700 to my HSA this year but i've tried to fill it in multiple times and it comes back saying I contributed $0. I don't understand this.

[BMcCalpin]

If you contributed $2,700 through your employer, then this is correct.

If either your employer contributes or you contribute through payroll deduction, then (1) this amount is reported on the W-2 in box 12 with a code of W, and (2) this amount is removed from Wages in boxes 1, 3, and 5 before the W-2 is printed.

Thus, there is no "deduction" for this kind of contribution, because the contributions were never in your income in the first place.

Only if you made direct contributions to the HSA (NOT through your employer) would you see a deduction on line 25 on Schedule 1. Note that the HSA MSA amount on the Deductions & Credits screen show only the direct HSA contributions, not the code W amount.