If your offer letters are generating without substituting the offer token for the expected offer values, it's likely that the text in the offer letter isn't being recognized as a token.
To resolve this issue, open the original offer template and remove the token, including the spaces before and after the token. Manually retype both the token and the spaces in the offer template.
You can then save these updates to the document and upload this new document to Greenhouse Recruiting under Configure 
> Offer Templates.
After uploading the template, click Test to verify that all your tokens are valid.
You can then create a new offer version for your candidate, which will allow you to generate a new offer letter using the updated template.