there are two reasons for this problem: first, when the content of the page has not been completely downloaded to the local area, clicking trigger to run a certain program, but this program can't be found. Second, because the control cannot be downloaded locally, this error will also be reported when the script in the page calls the control. At this time, it can be solved by manually registering the signature control.

try saving this dll file in the system32 directory of the system again, and click start-run the execution command "regsvr32 downloadfile.dll".