You may have added too much water, most of the references I have seen say to add no more water than 50% of the volume of seeds + juice. For most tomatoes, the juice you can squeeze out will suffice; I have never had to add water. If the tomato is very dry (I have a few that are) or if the seed quantity is very small, strain the juice from a juicier tomato (to remove the seeds) & add it to the mixture to increase its volume.

Also, a week seems like far too much time. The gel will be destroyed by fermentation in 2-3 days, or even as little as 24 hours; the warmer the area, the more rapid the fermentation. If the seeds are not removed promptly after the gel breaks down, they may begin to sprout - I've forgotten a few batches and had this happen (it only took 4 days). Such seed will die quickly once dried, and should be discarded. Examine the seeds under a magnifying glass; you may see a small dead sprout on the pointed end of some of the seeds.

It is possible that there are still a few live seeds. You could place a large number on a wet paper towel, and watch closely for germination - then immediately transfer any that sprout to moist seed starter. But if seed is still available, it might be best (and far easier) to start fresh.

Thanks, zeedman. I'll be following your advice this season and will try the rest of my seed to see if any survived.