I've been a Google AdSense customer for 5 years now. My site is https://wranglertjforum.com. It generates around 1.5 million page views per month and 231,000,000 ad impressions per month. I've never had a problem with serving ads until the past several months. My AdSense account has now started limiting ads and showing me the following message: Ad serving on your account is currently being limited due to invalid traffic concerns. We’ll automatically review and update this limit as we continue to monitor your traffic. Learn more about ad serving limits. What you can do Make sure you understand your ad traffic and site visitors. Never click on your own ads, and avoid partnering with untrusted or low-quality parties. Learn more about preventing invalid traffic. While this ad serving limit typically impacts publishers for less than 30 days, it may take longer in some cases. Now I've looked into this high and low and I honestly can't figure it out. 98% of my traffic comes from the U.S. as evidenced by my Google Analytics account, and there is absolutely nothing nefarious whatsoever going on. I've also made sure that ads are not showing in places where they can accidentally be clicked very easily, and on pages such as the registration page, login page, etc. Near as I can tell they are limiting ad serving based on nothing. I waited it out (14 days) and then the error message went away, then ad serving came back 100%. Within 2 more weeks the error message was back and they are now limiting ad serving again. It appears this is some sort of yo-yo thing going on and unfortunately it's impossible to get ahold of Google. I'm hoping someone might be able to tell me what I might be missing or what worked for them? This keeps happening and it's very annoying.
It's quite possible your bot traffic is out of control (not an uncommon problem for a forum). Your Google analytics may not pick up on that. Just a thought.
Cloudflare provides excellent protection when it comes to bot traffic. I've never used them myself, but anything I read about them sounds great. It does require changing the nameservers.
About 6 years old. Okay, I'll look into this. It sounds like they may be able to mitigate bot traffic.
I solved it by using Sucuri and their WAF. It got rid of an insane amount of bad bot traffic I had going to the site which was the reason Google put my Adsense account on pause. It's been months and all is well now, thankfully!