You are getting those errors because the RME_Mech_Piping_08_i.rvt is looking for the Arch_Struct file in the wrong place. The tutorial is obviously designed around a file structure that they did not fully maintain throughout the process. Grab the architectural file from that Arch_Struct folder and copy it to the same file location as RME_Mech_Piping_08_i.rvt. That puts the file in the right place. I assume that for any tutorial you'll need to again relocate that architectural file to the appropriate folder the working file is located in. All those training files should have been built to have the architectual file associated with them be pointed to the Arch_Struct folder which is part of the downloads.
On a separate issue, I still can not locate the "systems-default.rte", "mechanical-default.rte" and some others the training videos ask you to utilize. I have searched all availble download zips and I can't find anything.
Any help locating these files?
I think you solved this by yourself somehow but, up until today they still haven't fixed the path problem in the tutorial. That among other issues. Just in case, I solved the problem by reloading the link.
1 - Click try to solve the problem
2 - Click reload from
3 - Locate the file "Arch Link Model_m.rvt" locatec in the folder "Arch_Struct_Link_Files_m" in the folder of the tutorial.
4 - After thet, click to accept all and... Voila! the file loaded properly.
It's been ages since you had this problem but, "maybe" (he, he, he) someone else will also have this problem.