Why am I getting this error message when approving a solution? Kudos button doesn't work either

When I click the 'approve as solution' button, the solution doesn't get checked/approved as the solution. Instead I get the error message screenshotted below. Also the kudos button doesn't work - kudos just stays at zero. IT support at my organization confirmed that my browser supports Javascript and that Javascript is enabled. I definitely click the appropriate buttons to approve the solution and give kudos, I don't use the action URL directly in the browser address  bar.