DNG 6.0.3 - Import reqIF file: error "ForbiddenException: CRRRS8658E The server cannot validate the User attribute with the ****(some user id) value"

Hi to all!  I've exported a reqIF file from CLM 6.0.3 and I've tried to import it in another CLM 6.0.3 on a different server.  Import operation has created folders, but no artifacts or modules, the error was "ForbiddenException: CRRRS8658E The server cannot validate the User attribute with the ****(some user id) value". I've seen also rm log, but it contains the same error.
I've tried also to create an user with the same user id, to add to project area with the role of "Author", but it doesn't work.
Can you help me please?
Simona