What about his day time naps? Can he settle on his own? Are you open to try any sleep training method? Usually for that you would start with a good bed time routine, followed by any of the sleep training methods. 

I have the same issue. My 15 months throws tantrums whenever I leave the room. She used to be fine with me leaving, but recently, she’s been very clingy and gets upset easily. We’ve tried reassuring her and giving her a comfort item, but it hasn’t improved much.

Separation anxiety is common at this age. Practice short separations, reassure her that you will return, and gradually increase the time you’re away. Consistent routines and leaving her with a familiar caregiver can also help ease her anxiety.