Unsuccessful Pet Insurance claim

I have had an ongoing situation with the claim for my dog's (Bella) illness. It started in July 2021. At that time I was advised that I can't claim as the VET has not made a diagnosis as yet, and I should resubmit all documents when he makes a diagnosis. After getting a letter from him regarding the diagnosis, I resubmitted all the documents and medical histories again. And again I was told that they need a definitive diagnosis, once I have received that, then I should resubmit all documents relating to her illness again. I then took her to a different VET as the current one seemed to be useless and was unable to tell me what was wrong with Bella after doing all his tests,and she still wasn't better. The new VET was able to figure out what was wrong and treated Bella and she seems to be all better now. So again I submitted all the claims as instructed by the previous consultants. Today I receive a phone from Outsurance that they will only be paying the last invoice that has been submitted with all the other invoices. I was told that I shouldn't have sent these invoices as it is now past the 30 day mark, which means I can't claim for it and that the treatment she received from the other VET was unrelated.

Each consultant I dealt with instructed me to resubmit all documents for the claim regardless of date of service All these claims was related to making the current diagnosis. The VET used those test result to assist her in her diagnosis. It does not make sense why it would be rejected. What's the point of having Pet Insurance if your claims get rejected even if you follow the consultant's instructions.