Attempted delivery but not actually attempted.

So I've had a long string of issues with my local post office. I live in a fairly rural area. I also live in a HOA with instead of mail boxes at our homes we have a cluster of essentially P.O. Boxes where we get our mail. Now the issue is any time we get a package from anywhere, typically Amazon it seems like it never even leaves the post office. Post office opens at 8 I get an alert around 8:05-8:15 that the package is undeliverable. "Too large for mailbox" Even when I've been at the mailbox cluster and there's no carrier there. I can understand since we have smaller boxes for letters and such. But we also have a giant row of massive mail lockers for larger packages. They just never get utilized. I've gone to the post office and spoken with the person in charge, it's gotten me nowhere. I've also filed 2 complaints via USPS website after I was told there was nothing she could do "I can't keep track of what all my carriers do." Those have gotten nowhere 1st time about 2 years ago I got a follow up call and they said they'll look into it. This time about 2 months ago I didn't even get that. So I guess my question after my rant is where do I go from here? Amazon said they really can't do anything about it. USPS doesn't seem to care nor do the employees at the local office.