This is a very basic suggestion, so apologies to anyone who has already tried this, but I've been having some issues in Google Chrome lately that has been contributing to having my printing hang in certain Portal web mapping applications.
To see if this is what is causing issues for you, and you're using Google Chrome, you may want to first confirm whether or not the issue persists in Incognito Mode (use a similar privacy mode in a different browser).
If the issue does not persist in Incognito Mode, go to Google Chrome Settings > Advanced > Privacy and security > Clear browsing data, and clear your cache there. You may also want to clear other items like history, cookies, etc. If you're using a different browser, the steps should be fairly similar. Doing "Empty Cache and Hard Reload" in the browser/tab session doesn't seem to work on my issue, but clearing the browsing data does.
I have a hunch that maybe updating your web map application in Web AppBuilder Developer Edition can cause this issue. I updated several applications from WAB version 2.7 to 2.11 and then started to experience issues using the Print Widget on those applications. The one application I updated from WAB version 2.10 to 2.11 did not seem to have this issue.