"Cannot" is a pretty vague description. It tells us nothing about your service type, connection or environment.
Start here, verify and confirm the following steps:
If this doesn't help, you'll need to provide more more information about your phone service, how your device is connected, if you are using in conjunction with an answering machine, and fax configuration settings. Any additional observations, what you tried, what worked, what didn't, and any troubleshooting steps would also be helpful.
Bay Area - CA
~R5 C (188.8.131.52) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel 8 ~CarePaks Are Worth It
We would be happy to assist with the issue. To provide some feedback or some troubleshooting steps, we would need some additional information. If you could reply to this message with the information below, we can provide some assistance.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.