SKULabs requires either 25MB or 50MB of what browsers call "site data". The calculation for how much a single website is allowed to use is complicated but depends on the available space on the device; the usage by other websites apps and advertisements; and other factors which can be resolved by a restart of the browser and/or computer.
The first trouble-shooting step will be to clear your browser's cache and site data (includes cookies).
For Chrome: https://support.google.com/accounts/answer/32050
For Safari: https://kb.wisc.edu/helpdesk/page.php?id=69468
For FireFox: https://support.mozilla.org/en-US/kb/how-clear-firefox-cache
For Internet Explorer 11: https://kb.wisc.edu/page.php?id=15141
For Microsoft Edge: https://www.bitdefender.com/support/clear-microsoft-edge-cache-1914.html
After clearing the cache fully close down all windows of your browser and restart the browser. This can be tricky to actually do, most browsers sit idle even after closing them.
If you still can't sign in, restart the computer to be completely sure the space has been reclaimed.
If after restarting your computer, you still receive the Quota Exceeded error at sign in, you will want to check the available disk space on your device.
If you find your disk has at least a few gigabytes of storage space available, you can try your browser's "Private", "Incognito", or "Private Browsing" mode. Occasionally, an extension can interfere with our use of storage space on your device and this usually disables most extensions.
Finally, try switching to another browser temporarily to see if this resolves the issue. We have users report success with this, and they can usually switch back to their preferred browser after a short amount of time.
If you're still having issues, use the orange chat icon to start a chat with us and we'll walk through additional steps we can take to resolve the issue.