1. How long has it been?
2. Is it warm enough? This article says it should be 70-80 degrees. You might have to use a candle warmer or something to keep it warm enough.

Fermenting Seeds-found on the internet

Choose tomatoes that are fully ripe and have the best characteristics for their variety. Slice the tomato in half across the middle. Squeeze the seeds and juice into a clean glass jar. You can also scoop seeds from a tomato you are slicing for immediate consumption into a jar. Add water if the seeds are not covered in their own juice.

Label the container with the tomato variety and year of harvest. Place the container where children or pets will not disturb it. Choose a location where the smell will not bother you, such as a garage, greenhouse or outdoors.

Allow container to remain at room temperature until a layer of fungus has grown across the surface. Fermentation will happen within one to three days at temperatures of 70 to 80 degrees F. At cooler temperatures, the fermentation process could take a week.

After Fermentation
Remove seeds from the water when fermentation is complete. Add water to double the mixture. Stir vigorously. Good seeds will settle to the bottom of the jar.

Pour off the water. Pour out floating hollow seeds, mold and any debris with the water.

Add water. Pour off the water and hollow seeds again. Repeat this process until only clean seeds remain.

maybe too much water.

Ah, :( it was a both too much water and it was in an area that was too cold. Thank you guys for the info. When I saw videos on how to do it, they never really mentioned the temp or the amount of water.

If it's any consolation, it probably still managed to ferment. Just slowly and less scummy than usual.

If you can't save new seeds, keep those and do a germination test before you plant. They'll probably be OK.