Building lighting taking too long

I have imported a 3ds max model into UE4 ( 4.20) and when i tried to build the lighting it takes like forever by stucking at 0 percent. at the begining i got an error that i solved it by adding " lightmass Importance Volum" as a box around the whole seen. I tried to change then name of the folder save and didnt work. I looked at Swarm agent and here is the weird thing :

brown lines " Cashing irradiance photons (9202.4 seconds)" followed by Black lines " SkyLight Radisoity ( 1853 and counting).

is there anything wrong I have done here ? I would appreciate it if somone had faced the same thing before .

PS : CPU usage is 100 percent ( Core-i7) with 32G of Ram.