That’s in a gray area. It’s said by Brave that using a VPN in itself is not something that can get your account flagged or anything. However, it’s also said that using VPN to appear in regions you’re not can contribute to it. This is because ads are served to you based on your IP address. So using VPN to appear in other region has you see ads you shouldn’t be seeing.
So can it contribute? Yes. Do they say it’s enough in itself to get you flagged or cause problems? No. The safest thing to do is to make sure VPN is always for the country you’re in. So if you’re in USA, use a USA VPN. If you’re in India, use India node.
The biggest issue comes from what can seem like abuse. For example, let’s pretend you’re in a place like Turkey (13 campaigns) or Peru (15 campaigns) which tend to have few ads and use VPN to appear as if you’re in the United States (57 campaigns) or Canada (40 campaigns). It can measure as if you’re trying to cheat the system to get more ads, especially if you’re consistently connecting to VPN in those countries for extended periods of time.