Hi Alain,
Well if your configurations are correct and then you are not able to log into your target system, then there are 2 places which can go wrong:
1. You did not place clientaccesspolicy.xml and crossdomain.xml in your TARGET systen.
2. Your restgui settings for your TARGET system is incorrect.
Please verify your configurations based on here:
If the problem persists, then upload the HAR file too as described in the client side debugging link provided above.
(If its an URGENT customer matter, please create an OSS message.)
Regards,
Sushant