1st Time Installation of Pro today says "30 day trial is over. BUY NOW".

I set up the trial version of Avast Pro today. This is my first time using the product on a new computer. After installation, a pop-up said that Avast was disabled. Then the Avast window bar turned red an said your 30 day trial is over, BUY NOW. I had an expired McAfee trial on the computer, so I uninstalled McAfee thinking that it was causing the issue. I uninstalled and reinstalled Avast and I’m getting the same message that the 30 day trial is over and I need to buy it. What could be causing this error? (Thank you.)

Did you use the removal tool for McAfee prior to install avast ?
http://www.ache.nl

No, I forgot the expired McAfee trial was on the system, so I didn’t use the removal tool until after I’d installed Avast.

I suggest you remove McAfee and avast completely through control panel and then run the removal tools.
After that perform a clean installation and avast should work as expected.
A list with removal tools/instructions (from the developers) can be found at :
http://www.ache.nl

Many thanks, Eddy!
I’ll give it a try.

As an avast user like yourself and long term user and time spent on the forums.

The problem is, as far as I can recall, having uninstalled avast that would be considered as terminating the trial period. This would effectively throw up this error, some time ago it was possibly to reinstall but the trial period would be restricted to 7 days. I don’t know if that is still in force.

The OP should be fine after removing and installing avast again.
Removing avast should not end the trial period if he reinstalls avast again within that period.
But we will see.

That hasn’t been the case in the past, uninstalling the trial version has been considered as terminating the trial.

So we will have to see, the point of my post was to make it clear to the OP that this could be the outcome having uninstalled the trial version.