In the Chromium browser (and not only the one I believe) sometimes the 400 error can happen.
There are two solutions: first, most simple – just to clear all data via Settings => Clear browsing data.
The second one has googled on Reddit here>>> with a hint that the error appears because of the The Great Suspender plugin (nice and useful plugin btw).
The error looks like this:
Now – press F12, open Developer tools and reload Youtube tab.
In the Dev tools check the Application tab, select Cookies, on the left side and make a search by the “gs” (Great Suspender):
Delete all its cookies and reload the page:
Done.
