Got it.
I don't know why but the enum
backendproject.datastoreenum.reportingstore is the one causing the problem
guid projuid =
new
guid("31b50902bc474759a4cd08d549805500");
string
projname = projectclient.getprojectnamefromprojectuid(projuid, backendproject.datastoreenum.reportingstore);
I tried other functions and they do work.
Id