Short answer: Not really. If there's a custom Apex endpoint involved (which there usually isn not), you could see if the class is using the with sharing keyword and remove it - but that is highly not recommended. Especially in this particular use case. And it may not fix your problem.
First check to see if that user has API enabled. If they don't, there's nothing you can really do - they won't be able to hit the SOAP API. They'd need that perm.
Second see what fields the app is using and check Field Level Security against them, that is also a frequent culprit.
You can also try setting up a debug log as the (sales agent) user and see if obvious errors show up.