There is an org-wide, 24-hour rolling limit for REST API requests.
|The REST API request limit varies based on the version of Salesforce you are using.
|If you exceed the REST API request limit, you can’t sync and must complete one of the following:
To view the limit for your org,
The Attachments feature in FieldFX has been deprecated and replaced with the Files API. To upload files to tickets or jobs, make sure the FXL File Viewer Lightning Components is added to the ticket or job record page.
Follow the steps in Set Up Attachments Using the Files API.
There is a per user, per app, per hour limit for Chatter REST API requests.