Look on your Debugging IP Addresses page. CF11 I believe defaults this to localhost addresses only whereas prior versions didn't.
I was going to suggest the same thing, but I'm not familiar with CF2016 CFAdmin, so didn't know if that could have been the issue.
In the CF2016
Debugging & Logging > Debugging IP Addresses
Specify the IP addresses that should receive debugging messages, including messages for the AJAX Debug Log window. To include an IP address in the list, enter the address and click Add. To delete an IP address from the list, select the address and click Remove Selected. When no IP addresses are selected, all users receive debugging information.
They were defaulted to localhost /127.0.0.1 but I removed all of these so all users should receive debugging information.
I also have tried putting in my IP address (Specify the IP addresses that should receive debugging message). That didn't work either.
I also removed the global error template from CFAdmin.