A/C condensation into garage

I recently had a 14 SEER Trane system (heat pump & variable speed attic air handler) installed in my Clearwater, Florida home. Recently, the secondary condensation drain pan has been overflowing into the garage through the drain line. The installer's technician was out last week and cleared the outside drain line and at my request checked for problems inside the air handler, finding nothing. The drainage into my garage persists!! Any ideas?? I plan to call them back out tomorrow.
Thanks for your ideas.
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