should be two sets of condensation pans. The top one is the primary one, the second is the last chance.
When is the last time you poured bleach into the pan to kill and remove all the algea and growth? This should be a regular thing just like changing the filters. Your drain pipe may be clogged or the hole in the corner of the first pan could also be clogged.
Check it out.
Shine a light in there and see what is going on. When you go outside or wherever the line dumps out, is it draining water when the unit is on? It may still be and the unit may be leaking because the water is overflowing the first pan or the second pan gave out.
Flush out the lines and clean the pans and do an inspection.
All this can be fixed by you if the second pan has not been compromised. If this is the case, you need help.