The Enterprise WSDL and Partner WSDL endpoints are below. 
Enterprise: <soap:address location="https://test.salesforce.com/services/Soap/c/43.0/OrgID"/>
Partner: <soap:address location="https://test.salesforce.com/services/Soap/u/43.0/OrgID"/>

Question: If the system that's looking to connect to Salesforce can only support API v21.0, I'm assuming that the endpoint simply changes to the following however, how can I understand what obstacles to anticipate between the two versions?
<soap:address location="https://test.salesforce.com/services/Soap/u/21.0/OrgID"/>
 

I have a scheduled job that stopped running yesterday. In trying to re-run the job I deleted the scheduled job and re-ran the script to execute the job again but getting the following error:
First error: Too many queueable jobs added to the queue: 2

I don't see any other apex jobs scheduled so confused as to how there could be a 2nd queueable job in the queue. In the meantime, I'm unable to kick this job off until that error has been resolved.

Please help!

Hello,

Looking for help creating a trigger that updates a custom object, Dispatch__c, related by a mater-detail relationship to the Case object. There are a handful of address fields entered on the Case object that simply need to be referenced on the Dispatch__c object when creating a new Dispatch record. The intent is to have the fields pre-populated with the data from the Case when creating a new dispatch record.

Looking for any guidance the community can provide.

Thanks in advance.

I am trying to setup an integration between FedEx and Salesforce so that tracking information (delivery status, delivered time, signed by, etc.) is brought in real-time from FedEx based on tracking #'s that are added to a custom object in Salesforce. I've gone so far as downloading the WSDL from FedEx and generating the Apex Classes. How do I now schedule a class that runs every 15-30 minutes or so to pull in the relevant information from FedEx? Apologize in advance for what may be a basic question but trying to stumble through this integration and hoping the community can help.