I have two users on Wikipedia created before there was common sign-on across different language Wikipedias.
On the Estonian Wikipedia, my user is this: https://et.wikipedia.org/wiki/Kasutaja:Peep
The global / English user is https://en.wikipedia.org/wiki/User:PeepP
I am not able to log in to my Estonian username as I do not know anymore which e-mail address it's attached to. That address is probably not functional anymore.
Can you change the e-mail address on the Estonian username (Peep) to be peep.pullerits@gmail.com? The accounts link to each other using interlanguage links, that should be proof that I'm the same user.