I keep getting this message when running Tixati.
Feature: Online Threat Prevention

The page "Website URL' has been detected with suspicious activity. It is not recommended to continue browsing this website.
Accessed by: tixati.exe

But I don't see any sites loading in tixati and the tixati browser is not active.
So, what's going on? Is my program infected? No other alerts are coming up in Bitdefender.

false positive. I think Tixati's update check might have caused that. Try whitelisting Tixati.

https://www.bitdefender.com/consumer/support/answer/13427/

C:\Program Files\tixati\

I ran a manual update on Tixati and the alert did not appear, so I don't think it's that.
But I don't think Tixati runs ads...does it? I've never seen it run ads.
It could be a misconfiguration on my part, but I don't see anything about the site in the settings.

tixati does not run any ads in the software.
bitdefender is giving you false positives.

Tixati will connect to UDP and HTTP/HTTPS trackers. HTTP will, without a doubt, be considered a "website access". HTTPS less likely to be. In a broad sense, "website access" can actually mean "this program makes a sends traffic to an IP that we have on a blacklist." And in case of Tixati/BitTorrent it is certainly a false-positive. Bittorrent clients can't have malicious activity. You either download or upload. Doesn't matter the reputation of the IP address of the peer or tracker.
PS: Technically if there's a Remote Code Execution vulnerability in a client, it can be used for bad stuff. The chance of this is miniscule.