Short Term Disability: What info or medical records helps approval?

Hi all. I've searched previous conversations and see a number of you have been on short term disability for your jobs, but I don't see my question addressed so here goes!

I've had long COVID for about 10 months now. I have PEM, and just learned a few weeks ago at Mayo that I have ME/CFS and fibromyalgia with the long COVID.

Up until then, I've been trying to work as much as I can, taking lots of breaks during the day, but pushing through fatigue every day and frequently pushing myself into crash states. I understand now that's harmful to my health and recovery prospects to do that. So I was advised to take some leave from work while I start in on these medications and work on all the materials from Mayo on how to improve my condition.

We've got great benefits, and my HR rep was confident I'd have no trouble getting Short Term Disability (STD) approved.

Well. The insurance company that manages our STD is scaring me. They want proof that I am unable to work, they want proof of my decreased functionality. Long COVID, of course, there's no test for it I can show them. There's no 'proof' of the PEM. They're asking my doctor for medical records, which she wants to discuss with me tomorrow before she answers.

Those of you who are/have been on STD, what information did you provide your insurance company? What words do I (or my doctor) need to say to them, what medical records will convince them?

When I get back to a non-crash state, I would not be able to both work *and* attend all these doctor/education/coaching appointments and work on making all the life changes recommended for improving my health. I would not be able to work as I have been, just working, without constantly pushing myself into crash states. As I am today, I literally would not be able to work at all - I'm still in a crash state from all of the travel several weeks ago.

Thank you!