Easy Integrations > Failed Calls menu item displays already failed REST services.
A related issue, latest trial date, retry count, latest status, as well as REST details (URL, Method, Headers, ...), can be found on this page.
Also, you can manually retry the request as seen below:
Retry Limit for Failed Rest Calls
When the rest call failed, the system retries to rest call again until it will be a success. You can define a retry limit for failed rest calls.
Go to Easy Integrations > Settings (EI) page and you can set Failed Rest Call Limit.
The default limit is 5