What was Tali's Paragon Interrupt?
As shown here, the option is that you make a dive to try to catch her.
But you miss.
The interrupt only causes Shepard to try and save Tali, but he/she won't be able to catch Tali in time.
To save Tali and get both, the Geth and the Quarians on your side see this other question. If you do not meet the requirements to make peace between the Geth and the Quarians, e.g. because you didn't import a save, you cannot have the Geth join you and save Tali at the same time.