may be you have already got the point ! yes, cisco has pushed some IPS rules to IPS database which blocks unencrypted RDP connections to windows servers or PCs.
(anyway, i guess that you have not enabled RDP to outside network because of frequent critical security bulletins on RDP releasing these days)
in case you need to have a RDP through cisco IPS after 25th may 2019 IPS update push, you must have latest update installed in OS or disable IPS rules (in IPS profile configured to filter your traffic) to enable traffic. if not you will get,
message. in case your option is to disable IPS rules, you can disable,
Note : its recommanded always to have OS updated with latest patches, updates and do not enable RDP to un-trusted networks.