RTCM message not received

[ciniminis1]

Hi there,
I intend to use SKPOS provider to receive the RTCM corrections to Ublox ZED F9P module. Unfortunately, the corrections are not received due to connection dropout:

[INFO] [1724336896.510572]: Connected to http://195.28.70.16:2101/SKPOS_CM_31
[WARN] [1724336930.014829]: Reconnecting because we received 0 bytes from the socket even though it said there was data available 5 times
[WARN] [1724336931.205640]: Received unauthorized response from the server. Check your username, password, and mountpoint to make sure they are correct.
[ERROR] [1724336931.207347]: Invalid response received from http://195.28.70.16:2101/SKPOS_CM_31
[ERROR] [1724336931.208659]: Response: HTTP/1.0 401 Unauthorized
WWW-Authenticate: Basic realm="SKPOS_CM_31"

The dropout is caused by the NMEA message not being sent over, as I communicated directly with the provider, who confirmed they had not received the NMEA message. The NMEA message on nmea is published by Ublox driver with ~ 1 hz freq and contains the GGA string.
To confirm the functionality and rightness of the NMEA message, I connected to rtk2go.com provider and successfully received the corrections with the same Ublox settings. Have any of you come across a similar issue? Is there a way to check that NMEA msg was actually sent to provider?