Need advice for crate training new puppy we were told was already 100% crate trained.

We just adopted a 4 month border collie mix, Roscoe, a couple days ago. He's truly such a sweet boy. Other than trying to get our cats to stop hating us and them being terrified of the new puppy, things are going well.

The biggest issue we're having is crate training. We were told by his foster mom that he was 100% crate trained. He slept in his crate every night and she had him crated between 8-3 when she was working. She said he may whine and be restless at first in a new environment but will settle down quickly. This is not happening. The first night he cried for a half hour after we left the room. My husband thought he just needed to get used to us, so he slept on the couch next to Roscoe. Roscoe calmed down and slept the entire night without issue.

We contacted the foster to see if there's something we could do to help him. She said she never had any issues like this when she had him. She said we needed to ignore him and he'd eventually settle down because this is a routine he's used to. She said not to comfort him because he'll learn that when he cries, we'll come.

So last night we gave him half a Greenies calming chew to help with a little anxiety along with another treat he always gets when he goes in the crate. He cried for an hour before finally calming down and going to sleep.

He's fine(ish) in the crate if he can see us. He's great when he's not in the crate. However, we have noticed he still freaks out when we leave the room even when he's not crated. So we're worried about possible separation anxiety starting.

Any tips? He needs to stay crated at night at least until our cats stop being afraid of him and accept him. they were here first, so we're trying to put their needs first by making sure they have rooms that are just theirs where they can relax. We also need to keep him crated when we're not home until we trust he won't destroy anything or accidentally hurt the cats (which isn't a huge fear since he adored the cats at his foster which is a huge reason why we chose him).