Hi Matt,
We now understand the root cause of this issue and have a workaround for you to implement. Essentially you just need to enable the 'Uploads' Capability on the Feature Layer View.
Please refer to the information below and let me know if this fixes your problem. We intend adding a Known Limitation note to our Documentation to explain this situation.
Thanks,
Brett
Known Limitation:
For Surveys published from the Web Designer to Portal 10.6, submitting a survey with an attachment (eg image) will give the following error:
This is because the 'Uploads' Capability is not being correctly added to the Feature Layer View when the survey is published.
*Note this Limitation does not affect Portal 10.6.1 or any other versions (10.6 only), and only when publishing from the Web Designer (not from Survey123 Connect).
Workaround:
Need to manually enable the 'Uploads' capability on the Feature Layer View. This can be done using the 'Update Definition' operation on the ArcGIS REST Admin API:
1) Log into Portal using an Admin account and navigate to the Feature Layer (Hosted View) - this was automatically generated when you created your survey via the Web Designer.
2) Click the View URL button for the Feature Layer View (bottom right of page):
3) Add /admin/ to the URL to access the ArcGIS REST Admin operations, eg:
https://machine.domain.com/webadapter/rest/admin/services/Hosted/survey123_4e9085065b374452be83ef434......
Click the 'Update Definition' option that has appeared as a Supported Operation at the bottom of the page:
4) Copy and paste the following into the Input dialogue and click 'updateDefinition':
{"capabilities": "Create,Editing,Query,Update,Uploads,Delete,Extract"}
You will see {"success" : true} when the Capability has been successfully updated.
5) You have now added the ‘Uploads’ Capability to the Feature Layer View, surveys with attachments can now be successfully submitted.