Q.My philodendron ‘rojo congo’ stopped growing
This past winter I brought it in from the cold. It started blooming, then it started losing upper leaves. They would slowly yellow, then fall off. It is spring and since no more frost is here in Louisiana, I took it outside. Been there a couple of weeks and no sign of new growth.

You mentioned what the plant looked like at the beginning of winter - what condition is it in now? What care did the plant receive over the winter in terms of lighting, watering and fertilizing? I am just wondering why it was yellowing and losing leaves.
What are the temperatures outside at the moment? Philodendrons don't tolerate cold temperatures for extended periods.I wouldn't have it outside just yet unless the temperatures are staying 60 and above.
I would carefully prune away the dead/yellowed material off your plant and follow the care plan outlined in the following article:
https://www.gardeningknowhow.com/houseplants/philodendron/caring-for-philodendrons.htm