If you reused the old lines, just pressure testing with nitrogen is insufficient.
I am at a disadvantage since I do not know what process was or was not used...but I can tell you that it is absolutely critical with R410a that the system be totally free of air, moisture, previous oil and/or refrigerant.
I have seen many techs chase their tail for years on a ac call when thet should have just reclaimed, cleaned, leak checked and recharged.
With your description you have either:
A serious leak, which should be evident with an electronic leak detector.
OR...you have blockage of the system resulting in a low suction pressure
You see I recommend starting at the beginning to make sure no preexisting issues come back to haunt you.
You can clean, leak check and balnce charge all in one service thus eliminating all those options as supect.