Can you unhook the line again and apply air pressure to see if it's clogged. And maybe unclog it.

@stax I removed and cleaned the old condensate pump but that didn't solve the problem. I thought the pump was bad so I replaced it, which I am now realizing wasn't necessary.

At this point, if I manually empty the pump reservoir (been using a meat baster) when it gets full, everything runs fine. Otherwise, the outdoor unit turns off.

There should be a check valve in the discharge to prevent backflow. If it's dirty it won't work. Take it apart and have a look.

@charles-ross-homes Assuming you mean the floating valve in the pump that checks the water level in the reservoir, it is clean. This is a brand new pump.

The float switch turns the pump on and off. There should also be a check valve in the discharge line that prevents backflow.

You haven't done anything to check the line. It's not the pump or the reservoir or the float. Move down the line to check the remaining components. Or call someone to come for $100 and blow the line out.

Update - I cleaned the vinyl line and put the old condensate pump back. Everything is running normally now. Not only was the line clogged, the new pump seems to be shot.

I love this forum, thank you all for the advice!