[CURRENT ISSUE] Sims 4 Unable to Start, Already Running

reset you computer then try this

Okay, this is how I fix this problem. 

You will need the following mod for this to work MC Command Centre.

1. Go into another household
2. On the mail box right click 
3. then click MC cheats'
4. The click Sims/NPC Households Cheats
5. The click Summon sim.
6. Find the sims in the household you want to play and click on them and they will turn up at the current lot.
7. The right click the sims you want to play 
8. The hit MC Command Centre and click MC cheats.
9. There should be an option to Play this household.
10. Click and it will load you to that household.

Please let me know if that helps.

If you need a video let me know and I will do one for you and link it here