First, they might be lying. I've had it happen that people tell me they've done something when they have not. Restarting is usually an easy one to verify, just check the uptime of the system.

Second, maybe they did everything right, and actually restarted, that's cool that they tried something before calling in. I appreciate that.

Third, if the second thing is true then, I'm now frustrated, because now I have to get dirty with whatever is happening since a reboot that should have fixed the problem, didn't fix it. I know it's not going to be an easy fix. Most of the time, I'm right, unfortunately.

I'm all for users trying stuff before calling in. But recognise that you don't, and shouldn't have access to some things. Sometimes that's administrator rights, sometimes that's a piece of software, sometimes it's the ability to turn off the AV/firewall.

It can be a lot of things. If you're not sure if what you're trying won't screw things up more than they already are, then don't do it. If it's something simple that you know how to do, go for it. If you happen to get it fixed, so much the better.

"Customer self resolved" is usually the fastest way to get a problem resolved. That's good for you, for me, and good for everyone.