ahh that might be an issue.
i think that when you did the upgrade you might have messed up with the namespace of the project, breaking the class information.
so now your bp can’t find the parent, or it gets confused.
i assume you stil have a copy of the 5.4 version (and you always should if you want to avoid problems).
try making the port again.
but start by copying the whole project to a new folder manually, then open with the new engine, and when asked click “more options” then “convert in place”.
or you can try by
close everything
then delete intermediate, binaries and saved.
opening the .uproject and change the version to 5.5.
then right click the uproject and choose “regenerate project files” or smth.