あなたに会えなくて寂しいです。
会えなくて残念でした
I am also sad that I cannot see you.
It is unfortunate that I couldn't meet with you.
母に会えなくて寂しい。
I miss seeing my mother.
It was unfortunate that I could not meet you.
It is unfortunate that I cannot meet you.
I am sad that I cannot see everyone.