These are the most common reasons why a client is unable to sign a contract template or agreement template they've received:

It is possible that your contract hasn't been properly "sent" in Bonsai.  When viewing the contract, you should see that the progress bar is on "ACCEPT" and that there are buttons to "Send Reminder"

For security reasons, Bonsai uses different tokenized URLs for each person receiving a contract.  Sometimes we see a user trying to share their own URL, which will cause the recipient to be redirected to a "Contract Not Found" page.

If you want to send a contract via URL, you must click the link "SEND VIA LINK" when you are in the process of sending it.

It's uncommon, but some people disable cookies in their browsers due to privacy concerns.  Unfortunately, this can cause many issues when using modern web applications.

If your client is able to view the contract but unable to submit the signature form, they may have cookies disabled in their browser.  For this, you can either ask them to enable cookies in their browser or you can manually mark the contract as accepted.