Hello Nilutpal,
I have exactly same issue while generating stack.xml file for my UI Add-on 1.0 installation in Netweaver Gateway system. We are Solution Manager 7.1 SP12 (ST level SP12). I am getting the error "Not able to get the target product version of the MOPZ transaction".
Even when i check my download basket all the files except UI Add-on related files are getting added.
Could you please share the solution you have followed to resolve this issue.
Regards,
Radhakrishna K.