I have a custom ActiveX control, written in the late 90s/early 00s, that is used for communicating with a proprietary pressure measurement device over serial. We were previously able to Excel (2002/2007/2010/2013/2016) to create custom workbooks wherein customers could connect to their devices. While the practice has fallen out of favor in recent years, a customer reached out to us about using Excel 365, and I have discovered that we can no longer load or insert our control into the newest version of Excel. I receive an error, "The selected file does not contain any self-registering ActiveX controls." The ActiveX is in fact self-registering. I have disabled all ActiveX restrictions within Excel. Does anyone know a solution to this problem?
