Are you ensuring you're selecting the right Action option? To use a template you need to select the "reply using a specific template", and not the "have server reply using a specific message" option. Once the template one has been selected
you should be able to click on the "a specific template" link, and then select it in the window that appears. If it's not listed as a system template, change the drop down to "User Template in File System" which then makes the browse button
available, and you should be able to find and select the template you want.
Note however, if your intention is to get the replies sent regardless of whether Outlook is running then you don't want to use a template, since that will make it a machine only rule. If you want it to run regardless then you need to use the other option
"have server reply using a specific message", at which point in the message window that appears you need to enter the text that you want to be sent. Also note, when entering the text in that message window, if you enter something into the subject
line then that will replace the original subject in the message that's sent, but if you leave it blank then the recipient will see their original subject line but with Re: before it.