Failed to load CanvasControl

Failed to load CanvasControl __DYNAMIC__ASSEMBLY__\IOTPro.SystemPromotion.PayNow

Into Location main_content

Threw Exception

f:\canvas\sites\the-iot-pro\v10.0.0\Public\__dynamics__\IOTPro\SystemPromotion\PayNow.ascx(768): error CS1061: 'ASP.__dynamics___iotpro_systempromotion_paynow_ascx' does not contain a definition for 'btnApplyDiscountClick' and no extension method 'btnApplyDiscountClick' accepting a first argument of type 'ASP.__dynamics___iotpro_systempromotion_paynow_ascx' could be found (are you missing a using directive or an assembly reference?)