As it says there, make sure you have an active Ad account in the same business portfolio as your Facebook Page, and that you’re an admin with full access to all 3 assets (business portfolio, facebook page and ads account).
If you check all these boxes, and have shared as instructed, then support will need to look into it to see what’s happening in this specific case.
When you contact them, I suggest you send a loom video explaining exactly what you’re doing, showing them that you’re admin on all 3 mentioned assets, and sending them IDs for each asset if you can. This will help them find the issue and help you faster.