My client says that they cannot open the document I sent for signing

Here are several possible scenarios (from poor internet access through expired transaction). The other three most likely scenarios are:

The signer is using and out-of-date browser when trying to open the document. A page refresh might help although a proper browser update is recommended. If that is not possible, using an alternative browser is always a good option.
The signer has MyDocSafe login details (they have signed a document via MyDocSafe previously and set up their free vault or they have a client portal or their own subscription account)
1. Ask the signer to sign in and click on the "Signatures" tab to view the document ("Sign now" option). If the document has "see email" tag, resend the signature request.
2. Check that the signature request did not expire or was cancelled
The signer has an expired MyDocSafe free trial account
1. Ask the signer to sign in and click on the "Signatures" tab to view the document ("Sign now" option). If the document has "see email" tag, resend the signature request.
2. Ask the client to click on the icon in top right corner and check for any unaccepted portal invitations.