Generating an incrementing counter

I am having trouble implementing incrementing a counter within a registration form. I followed the steps here: https://dimagi.atlassian.net/wiki/spaces/commcarepublic/pages/2143945489/Incrementing+a+counter and updated two user properties as reported here: https://dimagi.atlassian.net/wiki/spaces/commcarepublic/pages/2143958236/Custom+User+Data

but so far when trying to set the "count" the demo throws this problem: Validation Error: Problem with bind for /data/count contains invalid calculate expression [(#case/count, 0) + 1] Couldn't understand the expression starting with ...