The borrower is signed in and can see the package. They press Sign Now or the e-sign button and are returned to the same screen. No error appears.
Check the pop-up blocker
The signing window opens as a new window, so a browser pop-up blocker stops it silently. Support's phrasing: if they click and nothing opens, pop-ups are being blocked. Tell the borrower to watch the top bar of the browser — the block notice appears there — and allow pop-ups for the site, then click again.
Privacy-centric browsers go further. Brave with Shields on blocks cookies and pop-ups outright and the signing window never opens. Have the borrower turn Shields off for the site or use a different browser.
Try a desktop browser
This also often turns out to be eConsent that has not fully registered, and the mobile app is where it happens. The file can show eConsent as complete on your side while the borrower's session has not caught up. Having the borrower sign in on a desktop browser and work through the prompt there has resolved this repeatedly — the consent registers and signing proceeds straight away.
"Token is Required"
This is a distinct error with its own cause. In support's words: 99% of the time, that error message is a work or school or public network blocking the secure connection. Have the borrower retry on their own phone, off the work network. Do not re-issue documents for this — the package is fine.
Check the network generally
A school, workplace, or other managed network can also block the signing window from opening with no visible error at all. A borrower on a corporate or campus connection should retry on home wifi or a cell connection.
Check which borrower is stuck
Where several people are on the package, confirm who is actually blocked. It is frequently the co-borrower rather than the primary borrower, and that changes where support looks.
When to contact support
Send the loan number and that specific borrower's email address. Support impersonates the account and reports exactly what the borrower sees, which settles it quickly.