"Unable to process request - salesforce.com servers are temporarily unable to respond to your request"
The connection fails when testing the connection under the application links. The suggested solution for this is the: Failed to establish connection to remote system salesforce.error.NOT_KNOWN_AXISFAULT documentation.
If the suggested solution fails, check the logs for “503 Service Unavailable” and "Unable to Process Request - salesforce.com servers are temporarily unable to respond to your request” errors.
The connection is unable to be established successfully to Salesforce when performing ‘Test Connection’ under application links.
The ‘Failed to establish connection to remote system salesforce.error.NOT_KNOWN_AXISFAULT’ error is thrown, with additional logs pointing to “503 Service Unavailable Unable to Process Request - salesforce.com servers are temporarily unable to respond to your request” error.
Due to a site switch activity over at the Salesforce end, the public IP of the Salesforce login URL changes. Jira is unable to resolve the new IPs, preventing requests to be sent to Salesforce.
Verify with your Salesforce Team if there is a site switch activity conducted recently.
If yes, your Jira instance will need to whitelist the new IPs for successful communication.
For more information on Salesforce Site Switching, refer to the Salesforce documentation here.
5. What actions are required to prepare for a site switch?
If you already follow our infrastructure best practices by not restricting access to Salesforce IP ranges and by setting your DNS timeout value to 5 minutes (default setting), a site switch should be seamless to your users.
Otherwise, if you are restricting access to certain IP ranges or data centers, update your network settings to include the complete list of Salesforce IP ranges in order to avoid any unintended service disruptions following a site switch. And if you control your DNS timeout values set, then you may need to refresh your DNS cache and restart any integrations following the maintenance.