Apparently, the error message that is displayed if you close and re-open Wealth-Lab Pro has been changed to say something to the effect of your account has been locked with phone number that transfers to Fidelity's general number rather than technical support. After much searching, technical support couldn't find any restrictions on my account, but apparently it took enough time that I could log in to Wealth-Lab Pro without any issues again.

This happened running 6.9.21.15 after trying to install an extension update.

This message is new to me but a rule of thumb is that Fidelity WLP account and verification is Fidelity's prerogative. This message coming from their back end looks like a glitch.

This is just a guess, but it may have something to do with either the frequency of re-login attempts or the frequency of failed re-login attempts. This is intentionally done to prevent hacking. Even Windows does it; the number of failed attempts (Windows logins) can be adjusted by enterprise Group Policy before Windows locks you out. (And if you're an enterprise Windows domain admin, you already knew that.)

But I've been doing lots of re-logins with WLP 6.9.22.7 lately, and Fidelity hasn't locked out my account yet--fingers crossed. I would check your WealthLabPro\1.0.0.0\Logs\wlp.txt file to see how many consecutive login failures it recorded. I know that WLP performs re-logins behind the scenes to keep your account active, but didn't think that background behavior was reaching some Fidelity lock-out threshold. Are you saying it is? Can Fidelity confirm this in their security logs? The WLP developers would want to know.

Are you running multiple instances of WLP (say on different [virtual] computers) all trying to stay logged in simultaneously?

And the other possibility is somebody is trying to hack into your Fidelity account. But this is the wrong forum for that. (You may want to change your password.)