Green card absence

Hello,

My husband has a spouse-based US green card/LPR. In August 2021 he went back to the UK temporarily to complete a Master's degree, due to the nature of the program and the expense versus what is available to him here. Originally we thought that the classes would be held remotely due to the pandemic, but he was informed that he would need to attend in person.

My son and I went to stay with him for most of his program as I work remotely for a US company.

The 3 of us came back to the US for a month in March/April during his semester break, then returned to the UK for him to complete his course.

He will be finished in August 2022. We've always planned to return to the US, but I didn't realize that we should have applied for a re-entry permit prior to leaving the US for him to complete his Master's degree abroad. I am afraid that, even though we came back for a month during this past year, he will lose his LPR due to the length of absence.

We were living in the US for 9 months prior to making the decision to complete the course, and only decided to do it because he needed to retrain as he was having trouble finding a job here. My husband has a joint US bank account with me.

Does anyone have any advice or insight, or similar experience?

Thanks.