Point them to this issue if you need to go to mediation, I suppose it will be accepted as an excuse to be late on your trade.
In a normal computer, it shouldn’t take more than 2-3 hours for a wallet with less than a year and not heavy use. If you open the terminal with Bisq, you can see how the process is going and get an idea if it’s still going on, but sometimes it can show as not advancing while it’s still worth to wait a little more.
You have instructions on how to proceed to restart Bisq and not losing the spv resync progress: Resyncing SPV file - Bisq Wiki
PS: If you have no Bitcoin network peers, spv resync will never work. Go to matrix www.bisq.chat for help on this issue.