If you have trouble with Plesk Migrator GUI, could I suggest you try Plesk Migrator CLI?
First, you need to configure migration - specify access to source and target servers:
Copy file %plesk_dir%admin\plib\modules\panel-migrator\backend\conf\samples\plesk-windows.simple.ini into <PLESK_DATA_DIRECTORY>\var\modules\panel-migrator\conf\config.ini, where PLESK_DATA_DIRECTORY could be retrieved from registry: reg query "HKLM\SOFTWARE\Plesk\PSA Config\Config" /v PRODUCT_DATA_D /reg:32
Edit just created config.ini and specify following options: ip of target Plesk server (in section plesk), ip of source Plesk server (in section pfw), windows-password - password of user Administrator on source Plesk server
Next, try to generate migration list - list of objects on source server, which can be migrated: domains, clients, resellers, etc:
cmd.exe /C "%plesk_dir%admin/plib/modules/panel-migrator/backend/plesk-migrator.bat" generate-migration-list
After that you can edit generated list (<PLESK_DATA_DIRECTORY>\var\modules\panel-migrator\sessions\migration-session\migration-list by default) - for example, remove some domains, that you won't to migrate, or reassign it to another vendors, and finally run migration:
cmd.exe /C "%plesk_dir%admin/plib/modules/panel-migrator/backend/plesk-migrator.bat" transfer-accounts
If you encounter a problem on any of these steps, please, let me know, provide log entries, and I believe, we can solve it.