I've been separated from my daughters mum for nearly two years. At first I had regular overnight contact and could facetime everyday and there wasn't a problem, then I started seeing somebody else, the ex stopped overnight stays at mine and stopped Facetime, I went to court to get a contact order, I now have my daughter regularly overnight and when she is with me she is absolutely fine. The problems start as soon as I take her back to her mums. She won't come near me or interact with me at all in front of her mum. I call everyday without fail but my daughter won't even say hello. On the rare occasion that my ex allows me to facetime my daughter will hide in the corner.
I'm really concerned and don't know what the best course of action to take is. Should I stop calling for a while? Do I persevere and hope it's a phase?
Recently my daughter said to her mum that she doesn't want to talk to me because I'm boring.
I let my ex facetime everyday that I have my daughter and she always talks nicely, likewise if my parents call to speak to my daughter she'll happily chat away. It seems its just me that she won't talk to.

I would be concerned that your ex, is talking badly about you, and/or saying things that would make the daughter afraid to talk to you, in front of her.

You may want to considering asking the court to have a outside evaluation if your ex is trying to cause issues.

Have you also tried a joint call with your parents, and see her reactions, to also get a third party opinion. You may also want to record those calls in case this goes further.

So don't be boring, use a media format that allows you to play a game together, or use some activity doing the call.

Three year olds don't have issues, they have phases. Your ex may be colouring your daughters mind but how much could she understand from that kind of input ? I would say take a break from this worry, Fr. Chuck has good advice and it comes from experience, ask for an evaluation and become less boring. I doubt a three year old knows what 'boring' is.