Has anyone figured out a solution for this? I'm experiencing the same thing now, so doesn't seem like this has been fixed. I published a survey from Connect (version 3.16) to AGOL. The row in my excel sheet is a file type with appearance as multiline. Then a constraint of count-selected (${field_name})<=10. This limits it to a maximum of 10 files.
When testing in Survey123 Connect, it works great. I can attach multiple files, up to 10. Just as intended. Then I publish to AGOL.
When I go to the survey on AGOL (web form), it only allows me to upload one file. I can't do multiple files. The Survey Settings is set to 'Use the version the survey was published with (3.16).' I'm also using this survey in an experience builder app and same thing, it only allows you to upload one file, not multiple.
I did remove the constraint and that fixed the issue. It allows for multiple file uploads across all products. However there isn't a file limit now, so end users could upload many files, which isn't ideal.