My hot tub is leaking water after filling it with water What's wrong?

2 years ago I had a serviceman for hot tubs shut down my hot tub so the pipes would not burst during the winter. The repairman serviced it again to reconnect the water pipe so I could use it this year. He noted there was mice activity and that the pump was a little tight. When I filled it up and restarted it the hot tub worked fine but water was leaking from the bottom and now I have a tub with a quarter of the water. Anyone know why it's leaking? Also shouldn't the serviceman have detected the problem before it was filled with water.