4 things about me (some of which might not matter):
* longtime Bitbucket user
* I change passwords on important accounts (inc BB, now therefore Atlassian) with period ~= 90 days
* I webbrowse with Firefox, and am currently still on Firefox version=56 (i.e., pre-Quantum) waiting for an extension to upgrade
* I run OS=Linux distro=Debian version=8.9
To change pw, I browsed to https://my.atlassian.com and attempted to login using what I strongly believe to be my correct credentials (including ID=email). I then got redirected to
https://id.atlassian.com/login?application=mac&continue=https://my.atlassian.com&token=<alphanum string length=280/>
[loop top]
which attempted to redirect again, which produced the Firefox warning
> Firefox prevented this page from automatically redirecting to another page.
I hit button=Allow, which immediately reloaded the page, but returned me to top of loop.
[loop end]
After ~20 trips through loop, I websearched on term='Atlassian login reload', which returned (et al) some helpful-looking material from domain=atlassian.com. I took what seemed to be the most useful advice, which was to
1. dump cookies
2. dump cache
3. reload browser
I did this, then rebrowsed to https://my.atlassian.com , but observed no change: same infinite redirect/reload loop.
What to do? Meanwhile, will retry on another box with Quantum aka Firefox version >= 57.