org.apache.commons.httpclient.RedirectException: Maximum redirects (100) exceeded An unexpected error has occurred. Your solution provider has been notified. (esign)

This error is caused by the Salesforce update to Deploy Enhanced Domains. If you have turned that on or if Salesforce auto updates it then you will get this error when trying to send a document to eSign.

Solution: You will need to update to the latest version of Opero Signature from the AppExchange here: https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000000q4LeEAI
This update will also update the Send Document page to lightning so you will then need to Customize the Send Document Page by doing the following.

• Click on the ESign Docs tab to view the Send Document page. 
• Customize the Send Document page by adding the lookup fields included with the app (Opportunity, Account) or your own custom lookup, text, or picklist fields.
• To add your own fields, first create the field on the eSign Doc object. Next, go to the eSign Doc Field Sets (Setup>Object Manager>eSign Doc>Field Sets>Send Document Custom Fields). Drag your custom field from the “Send Document Custom Fields” box down to the field set box below. The Field Set allows you to modify the Send a Document page layout by adding fields or reordering how the fields are displayed on the layout.