Please try to open a new Incognito Window and login to SeriousMD using that.
If it works, then that means you have a Chrome extension issue or cache issue.
Here's what to do with your original Chrome browser:
Just to make sure we eliminate malware from the scenario, please download something like Malwarebytes to scan.
Clear your cache completely.
Try resetting the Chrome browser to see if that helps.
Also, creating a new user profile on your Chrome can be helpful.
(Backup your bookmarks by exporting them as an html file to your desktop or documents folder or other) then, try resetting the Chrome browser to see if that helps
If the issue still persists, then there's a possibility of your browser profile being corrupted.
Quit Google Chrome completely.
In the Mac menu bar at the top of the screen, click Go.
Select Go to Folder.
Enter ~/Library/Application Support/Google/Chrome/ in the text field, then press Go.
Locate the folder called "Default" in the directory window that opens and rename it as "Backup default."
Try opening Google Chrome again. A new "Default" folder is automatically created as you start using the browser.
Once the new profile is created, try signing in Chrome and check if the issue is fixed.