Unconvincing

His explanation is unconvincing.

The argument is rigorous and coherent but ultimately unconvincing.

How many times have I explained to you that your explanation is most unconvincing?

The Allies made a very unconvincing attempt to help the Russians.

The judge thought that the witness's evidence was disingenuous and unconvincing.

Honest men make unconvincing liars.

Your arguments are unconvincing.

The proof Tom provided was unconvincing.

His performance was unconvincing.

Her explanation was unconvincing.