Pet insurance pre-existing condition

Hello,

Quick question about pet insurance, which has been a headache so far. Our new puppy developed a little limp a month ago. At that time, we were told it was a sprain and told to rest and take meloxicam. After that, we decided it was best to get pet insurance in case something in the future happens.

Well, the limp got better for a few weeks, and then came back, this time in both legs. After a hospitalization, many images, and blood tests, she was diagnosed with Lyme arthritis. We filed a claim with our insurance, which denied it as a pre-existing condition.

Is this something we can fight? The limp was there, but we can't prove that it wasn't technically a sprain since it got better for a bit. Are pre-existing conditions also considered such even if they weren't diagnosed before we started paying for insurance?

Thanks, and sorry if this is the wrong place to post!