Subsidiary account blocked, cannot unblock

[MrCurious2]

I have a subsidiary or secondary email account on my main email account.  Somehow I screwed up the pword and I've been absolutely unable to reset it.  I've tried everything, multiple times.  One thing I've tried several times is requesting a new (4 digit) PIN to be sent to my landline, but even when I get that and enter it, I cannot unblock the account.  (Tho, oddly, I have always been able to download email in that account via my Thunderbird software--until now, since I have changed to a new computer.)

And at this time I am away from my landline for several weeks, and I was (understandably) unable to enter my cell [phone number as an alternative.

HELP!!!!!!!  This problem is driving me crazy.