Video Issue- ISMv2 course

I Have A problem with running "some Modules" Video training for ISMv2 Online course

Videos Works well for the first 6 modules. For the 7th one, it has 4 videos

the 1st one "NAS Components and Benefits" works well

-the other 3 doesn't work

-Beginning from Module 8 to the last one "15th" all videos doesn't work. but PDFs works

It is annoying for me as I can't continue the course that way. I am waiting for a solution, thanks in advance