How to mask as Chrome
this is why
Chrome 27.0.1453.94 is the browser reported when using user agent switcher and it's more than likely they want to see a later version of Chrome
You may have more luck asking them why on their Face Book page
(from their support FAQ)
Do you provide support on Facebook?
Yes, we have a dedicated MateCat User Group on Facebook.
Interestingly, their site works fine in Vivaldi, Otter and Iron (without any user agent tinkering). Just not in Opera.