9 month old cries nonstop with Nanny please help me

Desperately need some advice, LO is 9 months old and will cry non stop with nanny all day. It's agonizing! Looking for some tips to help or others experiences. Background: I WFH and do try not too intervene, I only come in during lunch and end of day because I've read it's best not too reinforce the crying. We did hire a new nanny so he's only been with her for about 5 days now, he did fine with previous nanny before Christmas (but my husband and I were off for two weeks during this time watching him, so he may have gotten used to being back with us). I also think it may be separation anxiety related, but he does fine with my mom and MIL. Please help!