Webform Submission issue

We are currently using our own custom WebForm to submit directly to Smartsheet. This process has been working flawlessly for the last few months. We had had users reporting now that when they hit submit on our php WebForm the old Smartsheet WebForm pops up and is completely blank. However if we go into Smartsheet, all the data they entered on the form has been posted to the correct Smartsheet form.

Here is our submission code.

included in screenshots

Can anyone give us some insight into what we may need to change to get this issue resolved?

Thanks

Timothy Hasty