I have seen many people face this problem when they download and install IDM (Internet Download Manager). They are not able to see any extention in chrome after they install IDM.
Well If you want to solve this problem just follow my steps.
Table of Contents
Method #1
Go to IDM Settings and in General see to it that under the capture download from the following browser, chrome is ticked.

If still you are not getting your issue solved then use the next method.
Method #2
This method is very simple go to this link – https://chrome.google.com/webstore/detail/idm-integration-module/ngpampappnmepgilojfohadhhmbhlaek
Add this extension to chrome. After that you can see the IDM extension.

Now you can download video from chrome using IDM.
Conclusion
Thanks for reading our post. I think it might have helped you in fixing your IDM issue. If you are still facing the issue let me know in the comments.