Hi Lina,
I really didn't find a solution, just a workaround. The problem didn't happen on a Windows computer, so I told the student to use the teachers computer or his home computer to insert the pictures into his tour.
It definitely didn't work on the Chromebook. There were no issues with his GAFE account and I tried everything that was suggested in this thread.
My tech department was no help and told me to contact Google support. Lol.
I hope this helps. Any other suggestions are greatly appreciated.
Thank you,
Kim