In the case of having the b+ product installed in an ECC system that is going to be converted to S/4 HANA, the following must be taken into account.
Before performing the SUM process, both the original .SAR patches of the b+ product and their respective ACPs must be placed in the directory where the patches are uploaded.
ACPs are files that modify the requirements of the original addon to allow the installation of the addon on the S/4 HANA system.
In case the ACPs are not included, the SUM process will not allow the conversion and will display an error message indicating this in the corresponding component validation phase.