convert2rhel fails with unclear error message

I'm trying to migrate a CentOS 7.9 VM to RHEL 7.9 using convert2rhel.
This CentOS VM is not connected to the internet, so I created a local repository VM that contains the repositories for CentOS 7.9 and for RHEL 7.9.
On the CentOS VM that I want to migrate I have the repo files in /etc/yum.repos.d pointing to these local repositories.

After running convert2rhel --no-rhsm --disablerepo=* --enablerepo=rhel7-server --enablerepo=rhel7-extras --enablerepo=rhel7-optional --debug

it runs for a while, and then aborts.
The only thing that points in the direction of a problem is in the convert2rhel.log file. It says :

SystemExit: Only Upgrade available on package: gettext-libs-0.19.8.1-3.el7_9.x86_64

I do not understand this errormessage, let alone it points me to a solution.
Anyone here who has seen this before ?
I opened a support case, but this may be faster....