Can't play videos made by older camtasia 4 or 5

I made bunch of tutorial videos with Camtasia 4 and 5 in 2007 to 2009, 
exported to HTML with swf file.
I've been selling these videos to my customer.

I have never been had any problem but recently all of my customers complain to me that
they can't play any videos with any browsers such as Chrome,IE,Firefox.
I recommended them to upgrade flash player but problem were never solved.

Open html file but video never play.
I updated flash player then try again but same problem happened.

Now I'm suffering so many claims from my customer,
so please help me.

I guess something happened in Adobe's new flash player's feature,
it doesn't support the video made by older version's Camtasia like 4 or 5.