Can't change email address, No Dell Rewards, Incorrect Warranty Info Online

In Dec 2019 I ordered a laptop and 2 monitors, which I received.  Later I tried to change my email address to a different one and kept getting an 'email address not authorized' error.  Sent emails to Dell to try and fix this, got sent password resets which didn't resolve the issue, in the process somehow my account was inactivated.

Today I spent a lot of time on the phone trying to fix it, was told I needed to create a new account.  Tried it with the preferred email address, still got the error message about it being unauthorized.  Managed to create an account with the first email address, added my customer number, could see my purchases again, but nothing in regards to Dell Rewards.  I would think I would have some considering my sizable purchase.  Was told it would take 30 days, but it's been longer than that since the purchase.  There is also still incorrect warranty info saying on all 3 items the warranty expires in 90 days when I was assured in emails that it's 3 years.

My questions are this:

1.  Why can't I use my preferred email address without getting a 'email address not authorized' error?

2.  Why are there no Dell Rewards showing up since it been well over 30 days?

3. Why is there is incorrect information regarding the warranties on my purchases in the online account?

I like Dell products, but I have spent hours trying to resolve these issues now to no avail.  For a technology company I would expect better customer service and less technical errors on their site.  Customer service has not been useful with these issues except only to reassure in the email sent to me that my warranties are longer than what is showing up on their site.