Executable does not show icons

I have tested the .exe on approx. 10 computers and it worked fine. But now I have customer no 11 who can open the file but cannot see the icons on buttons. And clicking the buttons does not work either. He has a windows7 PC.
I do not have an idea how to solve that

PS: the customer received an error message:
http://heserver/js/ui.min.js
0 3:10943
expected: ‘:’

Looks like a problem related to Internet Explorer (IE) compatibility. What version of IE is your customer using? And what version of IE your compiled website is compatible with?

I do not know the IE version of my customer and will never know/cannot predict before he buys.
I compiled the version with html executable and Internet Explorer11 (update 11.0.33)

I have meanwhile asked the customer. He has never used the Internet explorer and never updated. He has IE8 installed.

that was the right hint with the internet explorer
I convinced the customer to make some tests for me:

IE8 did not work at all at the customer
IE10 worked 80%
IE11 works 100%

Now at least I have understood the reason of the problem.
The question is now:
is there a solution for customers with older IE installations (I do not know their version when they buy)