Using websocket_authentication_argp.py and the credentials provided by the refinitiv team, I tried to connect to UAT and got "Invalid Application Credential".

Have the credentials somehow expired, or did I misunderstand the usage of the credentials?

More details, obtained by running with --debug 7:

Sending authentication request with password to https://api.ppe.refinitiv.com/auth/oauth2/v1/token ...
('https://api.ppe.refinitiv.com/auth/oauth2/v1/token',
{'headers': {'Accept': 'application/json',
'content-type': 'application/x-www-form-urlencoded'}},
{'data': 'grant_type=password&username=GE-A-<censored>&password=<censored>&client_id=GE-A-<censored>&takeExclusiveSignOnControl=true'},
{'auth': ('GE-A-<censored>', '<censored>')},
{'verify': True},
{'allow_redirects': False})
https://api.ppe.refinitiv.com/auth/oauth2/v1/token
grant_type=password&username=GE-A-<censored>&password=<censored>&client_id=GE-A-<censored>&takeExclusiveSignOnControl=true
{'User-Agent': 'python-requests/2.18.4', 'Accept-Encoding': 'gzip, deflate', 'Accept': 'application/json', 'Connection': 'keep-alive', 'content-type': 'application/x-www-form-urlencoded', 'Content-Length': '152', 'Authorization': 'Basic <censored>'}
RDP-API Gateway authentication HTTP code: 401 Unauthorized
response : {
  
"error":"invalid_client",
"error_description":"Invalid Application Credential."
}