The error ‘ctrl_net_omnis_signature is not defined’ implies that this file has not loaded.
I have just downloaded 8.1.3 on MacOS and followed the instructions on GitHub to add jsSignature without issue.
I can reproduce this error if ‘ctrl_net_omnis_signature.js’ does not exist in my /html/scripts folder or if the appropriate line has not been correctly added to /html/jsctempl.htm so it’s worth rechecking these again.
Also note, the html folder used on MacOS is the one in Library/Application Support/Omnis/Omnis Studio 8.1.3 x64 (hold alt key in finder Go menu to view).
One other thing to check is that the double quotes used when adding lines to jsctempl.htm visibly match those already used in the file as there are different variations of these on MacOS.
Hope that helps….