Make sure the zoom lock is off. I think the adapter may need to talk to the camera via the lens which according to the manual would have a setting in the menu for MZ/PZ, manual zoom/power zoom. The manual talks about Canon EOS cameras and only mentions the EOS 80D, so you might be up against a compatibility issue.
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EOS C100 mk2 with a Canon EF-S 18-135mm IS STM, and a Sigma EF mount 10mm-20mm EX DC HSM wide angle - Zoom H2Essential - Dell 8700 i7-4790 3.6Ghz, 24GB Ram, Win 10, Nvidia GTX 1060 6GB - DaVinci Resolve Studio 20.3 - Blackmagic Speed Editor - Presonus Faderport 1.
