Be distraught by toddler's rejection of das

[EllaWt]

Hello
Our 21 months old daughter is being a nightmare with her dad. She just outright rejects him and everything he does and strongly prefers me. Her dad is the best he takes amazing care of her and he is a hands-on dad so it's really breaking my heart because I can see he'a hurting.
Has anyone gone through that? Is there anything I can do?
I should say i am 7 months pregnant with baby number 2 but this is distressing me greatly

I know that I was like this as a child. I was a massive mummy's girl and for some reason I never really bonded with my dad. My mum told me I would cry when he held me and I would always reject him.
I obviously don't know anything about this as I was a baby/toddler. There was no reason behind it. My parents were/are happily married, happy stable home, I have an older sister.... I think I was just so attached to my mum and had a lot of separation anxiety without her!
Not sure what the answer is but 121 time is probably the best starting point!