I don't know if you ever got this figured out, but I had the same problems & concerns. I was also happily running Fences4 on my Windows10 computer, but was constantly interrupted with flash screens that I also suspected were attempts to get me to upgrade. My pop-up screens were different — they asked if I wanted Fences to make changes to my computer. I was constantly clicking out of them. If you get a screen like that, click on the More Details button and you'll find there are 4-6 areas they point to. I finally resorted to ChatGPT with the problem and after much back and forth, I seem to have gotten rid of them (and will sleep well tonight knowing that I won't have to deal with it any longer. Who needs more nagging in their life?
). Depending on the way you have your computer set up, the steps you'll be given may not match what you're seeing on your screen. I'd just reply "there is no xxxxxx in that folder," and I'd get another work-around. I'm still checking to make sure all the notifications have been disabled since I only finished it about an hour ago. I don't know how your question to the forum popped up on my screen, especially since I hadn't consulted the forum, but it seemed like a good opportunity to share my fix. Let me know if I can direct you any further. Always glad to pay it forward when I can.
