As a Salesforce user, you will need to review and update app authentication settings, in particular your token refresh policy.
To learn more about how to configure a Connected App in Salesforce: Manage OAuth Access Policies for a Connected App
Should you have any issues with managing your Salesforce authentication policy, please contact Salesforce support.
Below is a brief guide to managing your Salesforce app authentication settings.
In your Salesforce account, go to : Setup > Platform Tools > Apps > Connected Apps > Connected Apps OAuth Usage
Locate the Ecanvasser App and click Install
Continue on with the app installation process:
Next, navigate to: Setup > Platform Tools > Apps > Connected Apps > Manage Connected Apps then click EDIT
Review your refresh token policy settings.
We highly recommend that you select "Refresh token is valid until revoked" as this options allow your Salesforce/Ecanvasser integration to remain in active without the need to re-authorise the integration on a regular basis.