F5 LTM upload a file issue

Hello,

I'm pretty new with F5 and I'm changing an old F5 for a new one, all seems to be good, I can access to all websites and applications, but in a website there is a pop-up window that allows to upload files, I can select the file then clicked in upload but it didn't work, the pop-up windows does not show any error message and in the F5 I can't find anything relate to this in ltm logs, the file is just not uploaded. I tried to talk with dev team to ask about the communication process, but it looks like they even don't know, so, I want to know if you have any recommendation regarding in how to do the troubleshooting in here?

I'll appreciate all your recommendations. Regards