Upgrade Nexus, I failed to initial signin "no admin.password created"

We have nexus nexus-2.14.7-01 and would like to upgrade to latest version of Nexus3.
I have test in test environment to install the latest version of nexus 3.28.0. Everything went well but the upgrade process needed to update nexus2 to latest version.
At this point I installed an older version of nexus 3 nexus-3.1.0-04 but the problem is that the initial log-in doesn’t work! I have tried other version and the same problem I get:
“GET /static/rapture/resources/icons/x32/house.png?_v=3.1.0-04 HTTP/1.1” 200 1722 3

I could reproduce the issue: on fresh Ubuntu I have installed Nexus Repository Manager 3.18.0-01 and the initial sign-in works, then i stopped the service and delete all nexus I have and installed Nexus Repository Manager 3.1.0-04 ang GET THE PROBLEM NO admin.password created! i can’t initially sign in.

I have tested with chrome and firefox, I have deleted the cache.

Can you please help me to figure out the problem

Please follow the Upgrading from Nexus Repository Manager 2 Guide.
tl;dr; Upgrade your existing 2.x to the latest 2.y. Migrate your new 2.y to the latest 3.z

There is no reason why you should be migrating using nexus-3.1.0-04, as that version is not the latest 3.x and it is not compatible with the latest 2.x. If you don’t have already any 3.x just go straight to the latest, but if you happen to already have a working instance of 3.x with data you want to preserve you have to upgrade to the latest 3.x before attempting migration.