I tried as you suggested, however I cannot have the
cyclic form of my protein.
That doesn't give me much information to go on, but if you send me your
input files, I can take a look.
I tried also writing differently the IDs ('1' or '1:' or '1:A')..
The example I sent you works, although obviously if your C terminus is
not at residue number 54, you'll have to change that. The N terminus
should always be 1, unless you have done something very unusual.