Desktop site suddenly switching to mobile view

Today I opened up my website (www.houserepublicans.wa.gov) only to watch it convert to mobile view - even though I was viewing the site on my desktop computer. My site is highly customized, I use a child theme, but I haven't made any changes to my child theme that would do this and I have not updated to the latest version of Catch Box. Currently I have 2.8.3 installed. Any help you can provide I would appreciate - the site looks terrible right now!