Trailhead Challenge: Guide Users Through Your Business Processes with Cloud Flow Designer (https://trailhead.salesforce.com/trails/force_com_dev_beginner/modules/business_process_automation/units/flow)

Problem: Even though my field has the correct label "Upload_File", the "Check Challenge" button keeps reporting that it cannot find the same. I have confirmed that my flow is "Active". I deactivated the flow, deleted the screen element and recreated the whole thing and saved as a new verison, but the problem persists.

I am unable to complete that challenge as a result.

Here's what Trailhead is reporting 


What should I do to proceed?

Trailhead Challenge: Guide Users Through Your Business Processes with Cloud Flow Designer (https://trailhead.salesforce.com/trails/force_com_dev_beginner/modules/business_process_automation/units/flow)

Problem: Even though my field has the correct label "Upload_File", the "Check Challenge" button keeps reporting that it cannot find the same. I have confirmed that my flow is "Active". I deactivated the flow, deleted the screen element and recreated the whole thing and saved as a new verison, but the problem persists.

I am unable to complete that challenge as a result.

Here's what Trailhead is reporting 


What should I do to proceed?

Trailhead Challenge: Guide Users Through Your Business Processes with Cloud Flow Designer (https://trailhead.salesforce.com/trails/force_com_dev_beginner/modules/business_process_automation/units/flow)

Problem: Even though my field has the correct label "Upload_File", the "Check Challenge" button keeps reporting that it cannot find the same. I have confirmed that my flow is "Active". I deactivated the flow, deleted the screen element and recreated the whole thing and saved as a new verison, but the problem persists.

I am unable to complete that challenge as a result.

Here's what Trailhead is reporting 


What should I do to proceed?

Not able to complete the challenge as "an unexpected error occurs" while verifying the challenge solution. 
Module: Advanced formulas
Unit: Leveling up with Advanced Formulas

Reference error id: BYFMQANQ