Being banned from seeing enforcement history, what does it mean?

The enforcement team doesn't uses the forums and we can't help you with suspension issues

To check your suspension or if eligible for a case review:
https://enforcement.xbox.com

You also have the option to check with the chat support to inquire if there is an enforcement action on your account and for how long. They can't assist with the enforcement actions, however they should be able to inform you on the actions present in your
account

My current enforcement does not appear in the enforcement history. What does this mean?

you will need to go to the following and sign in to see why you are banned

Enforcement history | Xbox Support

if you don't see anything and the console says banned then it's a hardware ban which means a new console.

The Enforcement team does not read or respond in the forums. The message your friend sent does look offensive if you have quoted it accurately, so your report of it will be taken seriously. The action take will depend on your friend's enforcement history;
if this is the first offense, there might be a one day/24 hour communication ban, for example.

I'm not sure what the "banned in a couple of days" means. The Enforcement team does not pre-warn of actions; there is either a suspension or there isn't. If that's an accurate mention, your friend might have gotten a message from somebody else (not Enforcement)
that has no actual effect on enforcement.

You can't get banned for watching Mixer, if you enjoy watching people streaming games then by all means feel free to do what you enjoy.

If you did get banned check the Enforcement history on your account to see why you received enforcement action. You may have just said something to someone through chat and got reported for it. The enforcement team investigates each report that is filed
and decides whether or not there was a Code of Conduct Violation or not.

There's nothing against just watching Mixer, so there's no reason to worry about being banned for it.