When using Salesforce Connect with an OData 4.01 adapter, the Validate & Sync operation may fail if the external OData service does not support a trailing slash at the end of the service root URL.
Per the OData 4.01 specification, the service root URL must terminate in a forward slash, and Salesforce sends the request accordingly.
If the external OData service is not configured to handle requests with a trailing slash, it will return a 404 error causing the sync to fail.
The external OData service must be updated to accept and respond to the service root URL with a trailing slash as required by the OData 4.01 protocol.
Reference Article(Service Root URL section): https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#_Toc31360927
The fix must be implemented on the third-party — their OData endpoint must support to return a valid Service Document when the service root URL is accessed with a trailing slash.
Reference Article(Service Root URL section): https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#_Toc31360927
005388911

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.