After upgrading a small project from 7.9.10 to 8.0.1 all the tags were lost, the tag provider was still there, but empty, after looking through the logs I found the below error, importing the tags from an xml export file worked, so the project is now working, but though maybe helpful to share this.
Attached is the wrapper log file and project tag xml files
INFO | jvm 1 | 2019/05/11 13:08:05 | E [t.s.internaljson ] [12:08:05]: Errror storing tag changes. provider=Local_RT
KLOND_Tags.xml (70.2 KB)
ProjectSetupTags.xml (9.2 KB)
UDT_Defs.xml (512.3 KB)
wrapper.log (2.9 MB)
It looks like what happened in your case is that udt parameters like {NetID_Offset+Modbus_Offset} did not convert. The parameter class was set to Integer, and the conversion system was expecting a String. In 8.0, we got rid of parameter classes anyway, so it comes down to getting these past conversion. I added a ticket with your tag export to see how we can handle this with conversion. One thing you can try on your own though: can you set the parameter class to String for parameters where you have some offset math? If the udts still work with string parameters, then you should be able to upgrade without hitting errors.
We use too this kind pattern for opc item for all our 7.9 projects.
Hope you can find a way for the conversion to 8.0 !
This issue was is fixed in 8.0.3.