The Documill Dynamo button does not appear in Lightning

If the Dynamo Button is not visible in Lightning Experience after adding it to the Page Layout, check whether it is visible in the Classic UI. If the button is visible in the Classic UI, it is likely that the option to override the custom settings in Page Layout for Lightning Experience is enabled.

In the Page Layout,  Salesforce1 and Lightning Experience Actions area, check whether the button appears the Buttons in the section.

If it is activated, you can revert back to the Defaults. The button should appear again on the page after that.

If the customizing option need to be kept, drag the button from Salesforce1 & Lightning Actions group into the Salesforce1 and Lightning Experience Actions area.