Invalid status code on Head request-need a workaround to get data

1. What is the problem? Be very detailed.
I have a community member who has collected data, but when he tried to send it he gets this error message "Invalid status code on Head request. If you have a web proxy, you may need to log in to your network." I realise this has been posted before but I have not seen a resolution that can be fixed simply from a mobile phone with simple instructions that a 65 year old community member can resolve at his own home. We didn't have any issues with the other 4 community members that downloaded the same on the same day.

2. What app or server are you using and on what device and operating system? Include version numbers.
The latest ODK (29/7/2020). Mobile phone is a HTC OPKV1 Model No HTC One M8s

3. What you have you tried to fix the problem?
Looked for answers on this forum but these are so technical that we can't understand them. Please reply with a step-by-step instructions.

4. What steps can we take to reproduce the problem?
Here are my exact instructions that he used to download to his phone. It all worked but then he couldn't send finalised forms back to me.
1. INSTALL THE ODK COLLECT APP ON YOUR ANDROID PHONE
From your Play Store
Open ODK collect > install

2. DOWNLOAD THE XXXXX GOOGLE DRIVE

3 dots >General settings >server >google account > Add Account
Username: XXXX@gmail.com
Password: XXXXX
I agree

3. PUT PHOTOS OF PLANTS ONTO YOUR PHONE

Go to Google Drive
Hold down your finger on the first picture to select it, then select all photos.
Go to the 3 dots
Download

4. PUT PHOTOS OF PLANTS ONTO THE ODK FORM

Go to your downloads folder (in My folders or My Files)
SELECT DOWNLOADS
Hold down your finger on the first picture to select it, then select all photos.
Select MOVE
Ø INTERNAL STORAGE
Move to ODK/forms/...Media

5. DOWNLOAD VOICE RECORDER FOR FROG SOUNDS

Check that you have the - voice recorder app - downloaded on your phone so that you can record frogs.

6. DOWNLOAD THE ODK FORMS ONTO YOUR PHONE

Now you can go to the ODK collector app
Get Blank form
Select > XXXXX.xml

Download selected
OK

7. FILL OUT THE FORM WHEN YOU AT THE SITE

Fill Blank form
and you should be able to scroll through the questions. Some you have to fill in and others are optional.
When you get to the end >SAVE.

8. SAVE AND SEND FORMS TO GOOGLE DRIVE

When you get back to mobile/wifi reception, you can SEND all saved forms. This goes to the Google drive account and I can access them at the office.

5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.
Is there a work around? If he can't send the forms, is there another way to get data off his phone?