If the active directories are different then the sysadmin role mapping with the active directory will be required to be updated
select SID, Networkdomain, networkalias from userinfo
where networkalias = ''
select SID, Networkdomain, networkalias from userinfo
where networkalias = '
Find the SID for the user to be mapped in the new Active directory
Whoami /user
Copy the new SID for the desired user and update the same in the userinfo table
update userinfo set SID='', Networkdomain = '', networkalias = '' where id = 'admin'