This message tells us about an incorrect setup of the C1DEFLTS TYPE=ENVRNMNT macros coded in the endevor defaults table.
In the table, each TYPE=ENVRNMNT entry defines an endevor environment. For each of them, the NEXTENV= parameter sets the next environment in the map route.
The problem is that NEXTENV= parameter for the environment noted in the message points to an environment which is behind in the path, creating a path loop which is not allowed in endevor.
For example, if you have environments, ENV1, ENV2 and ENV3, it's correct to define a map like ENV1->ENV2->ENV3 but, if you define a map like ENV1->ENV2->ENV3->ENV2 you will get this message since the map forms a loop (from ENV3 to ENV2 to ENV3 and so on)
You can examine your C1DEFLTS source to find the error, or can take an endevor options report and see the environment definitions on it. The report should be produced even after the initialization failed.
In a batch run, the endevor options report is taken by adding //EN$TROPT DD SYSOUT=* to the JCL
In foreground, you need to issue command TSO ALLOC FI(EN$TROPT) SYSOUT(X), get into endevor (just to display the first menu), get out and go to SDSF or equivalent. The report should be in EN$TROPT DD among the outputs of your TSO session.