I'm still fairly new when it comes to publishing surveys to Portal on our Enterprise server, but have successfully published one or two very simple surveys that can be accessed publicly through online. In this process I made the feature class first, published it to our server and then created a New Survey from a Feature Class in Connect. I did not add any choices, or select statements and left the format as it was from the simple feature service. This published well and as long as it is public, there has been no problem with people submitting surveys outside our organization.
I currently built a new survey, in the same manner - first setting up the feature class and publishing that to the server - but when I went to make a survey in Connect, I changed text fields to select_ones and have included at least 6 different choice fields. Publishing it onto our Portal was not a problem. This survey operated well in all environments once it was published (online, Connect and the Survey 123 desktop application). The problem is that no one can submit any data. When attempting to submit online the error message simply reads, "Failed to Submit" and when I connect to Portal on the Survey 123 app, I get an Error Code 500, Unable to complete operation (see image). The feature service is public and available to everyone, and the survey is set that everyone will be able to submit.
What am I missing that would not allow people (from within or outside of the organization) submit their entries? I imagine if there was incompatibility between the feature class and the survey design, I'd get an error at publishing, but I don't. Please let me know if there is anything else I can provide to help. Thanks as always!!