Hello @boris92,
there are 2 points to consider when talking about the support for the SPA504G phones.
First of all, these phones already reached EOL status according to Cisco back on February 29, 2024 and are considered obsolete since then. The official EOL statement can be found here:
https://www.cisco.com/c/en/us/products/collateral/collaboration-endpoints/small-business-spa500-series-ip-phones/eos-eol-notice-c51-741207.html
Secondly, the security certificate on these phones just expired on May 31, 2025 according to a support statement from Ringcentral that can be found here:
https://support.ringcentral.com/cisco-spa-eol.html
The expiry of the security certificate has severe consequences according to the FAQ section of this document:
This means that your Cisco phone configuration will become locked when the security certificate expires. The phone will continue to operate, but configuration changes will not function normally. The devices will no longer be able to authenticate with the provisioning server so updates will no longer be possible. If the device is factory reset or if the phone configuration in the Admin Portal is deleted, the phone will stop working.
Hence these phones need to be replaced asap.
HTH!
