ERROR: "Bad Request - Request Too Long" When Signing In To Microsoft 365 Using Work Profiles
When the following conditions are true: Using the latest version of Microsoft Edge browser. When the browser is signed in to any Microsoft 365 account. When browsing to any Microsoft 365 website. I receive the following browser error: Bad Request - Request Too Long HTTP Error 400. The size of the request headers is too long. When I sign in to any Work Profile, no matter the account/tenant, the moment I browse to any Microsoft 365 page i.e. any website that redirects via: https://login.microsoftonline.com/, I receive the error above e.g. https://office.com, https://admin.microsoft.com, https://portal.azure.com etc. If I sign-out from the Work Profile, everything works fine (i.e. I am presented with the usual Microsoft 365 sign-in dialogue for username and password, then 2FA code, then the expected page appears), if I then sign-in > browse > error ... sign-out, works fine, sign-in, error etc. ... consistently repeatable. Using 'Browse as Guest' or any 'Personal' or 'Work Profile' without signing in works fine. TROUBLESHOOTING ALREADY CARRIED OUT Deleted/recreated all profiles. Signed in / out multiple accounts on multiple tenants. Sync options > all, some, none. 'Automatic sign in on Microsoft Edge' enabled & disabled. 'Allow single sign-on for work or school sites using this profile' enabled & disabled. 'Automatic profile switching' all options on & all off. Deleted all cache/cookies, from all time in all profiles. Reset settings in all profiles. Completely uninstalled/reinstalled Microsoft Edge (i.e. Safe Mode > delete all files > all profile data> all temp files > all registry entries). Q1 What could cause this error, only when the Work Profile is signed-in? Q2 Aside from syncing settings, how would signing-in to the Work Profile effect OATH requests to https://login.microsoftonline.com/,? Q3 Has anybody experienced this or something like this before? Q4 Are there any troubleshooting steps I haven't tried?
