There is an extension that is useful if you have been playing Touken Ranbu and/or Kantai Collection and the old method is not working anymore.
It was first brought to my attention by a Touken Ranbu player who'd made a Youtube video for this cookie method.
Login into your dmm account and come back to dmm.com
First click on the cookie icon
Press on ckcy, change the number from 2 to 1, check host only and unlock and lock two times
Press on cklg, change the word from 'ja' to 'welcome', unlock lock unlock and lock two times.
Edit This Cookie is available for Chrome and Opera.
I have yet to find a cookie manager that works equally as well on Firefox.
I take no credit for this method.
I just want to write a written tutorial on this method.
This webpage has been tested for Firefox, Chromium and Opera. There are no significant differences between all three.