If your roof is TPM you are better off using the Alpha Systems line of sealers. Dicor can cause some swelling if used on a TPM roof material.
It is typically a good idea to remove as much of the old sealer as possible and then apply the new to get the best repair. If it is a small spot repair, a good dab of self level over the suspected site should do it.
I cracked my skylight last year while on o a trip. I used the flexseal tape as an emergency measure until I got home. It worked very well but you could see the tape. Got the flex seal liquid and fixed the crack and it worked well so far.