Unable to start migration: Migration hangs on Preparing migration popup

kb: bug Plesk for Windows ext: migrator ABT: Group B

Applicable to:

Migration is stuck at the very beginning with starting migration message and nothing is coming up:
On the target server the%plesk_dir%\var\modules\panel-migrator\sessions\<datetime>\config.ini file contains the following information regarding the user credentials for the target server:

CONFIG_TEXT: [plesk]
...
windows-username = "admin"
The specified user does not exist on the target server at Start > Computer Management > Local Users and Groups > Users

Incorrect build-in administrator user is provided for the migration, however no warning was shown.

This is a Plesk bug #PMT-3961 which is planned to be fixed in future Plesk updates.

Until the fix will be available, specify "Administrator" account for both source and target servers:

Connect to the target server via RDP
Enable built-in Administrator account in Computer Management > Local Users and Groups
Do the same steps on the source server to enable Administrator account
Log into Plesk on target server and cancel the current migration session in Tools & Settings > Migration & Transfer Manager.
Start a new migration session specifying credentials for built-in Windows Administrator.

Alternative workaround for migration via the command line or via GUI, without finishing current migration session

Log in to the target server via RDP.
Edit %plesk_dir%\var\modules\panel-migrator\sessions<datetime>\config.ini file: Replace admin user with the server's built-in administrator login user:
CONFIG_TEXT: [plesk]
. . .
windows-username = "Administrator"

Log into Plesk
Go to Tools & Settings > Migration & Transfer Manager and proceed with the migration.