There can be three main reason why yourself or your client is unable to sign:
User Error
More often than not the client has missed a step which is preventing them from completing the process, however you'll want to make sure you've correctly formatted the signature box. Once you've ensured it is proper on your end, review the steps with them (ie; name, date, signature) necessary to submit.
2. Signature Elements
Signatures can be set as Client Signature or Vendor Signature. There can only be one of each option maximum. If you have two client signatures or two vendor signatures then you will be unable to use the E-signature function. If either yourself or your client are unable to sign; please check the formatting is appropriately assigned to either a client or a vendor for each Signature Block Element within your document.
You can check this by following the steps below:
For Client Signature:
Double-click or click Edit on the Signature block
Check the Client Signature box
Click Apply at the top-right of the edit screen
For Vendor Signature:
Double-click or click Edit on the Signature block
Check the Vendor Signature box
Click Apply at the top-right of the edit screen
3. Using the Same Browser:
This issue would occur if the client was there in person and was trying to sign the Document on an internet Browser that is logged into Event Temple. If you are signed in on your Web Browser it will automatically assume you are the Vendor and will only allow you to sign as such. If they are there in person you will need to open the Document on a browser that is not logged into ET. Incognito mode on google is great for this. Or you could logout of ET and use the link to bring up the Document for the client to sign.