Can you please provide details about the extension name, browser version and device version this issue occuring?

Updated this in a comment in the script version 3.4

Thanks for detailed analysis!

Do you want to add the pattern like
// @include https://www.google.*/*tbm=isch*

OR
// @include https://www.google.*

Because the second option will probably make the script run on every Google page.

Updated with the latest version.
Tested with google.com, google.de, google.co.cr image sites. Let me know if any specific domain is not matched.

I understand your feedback.
I will update to match with google.tld to match with any top level domain.

Re: @navchandar:
Merging it and closing the issue

Re: @nljuggler:
Thanks for the update. Shall I merge it with the source code?

Re: @GuyInDogSuit:
Cheers 😊

This could also be an issue with Firefox Content Security Policy with respect to Tampermonkey. See a workaround here.

Re: @navchandar:
After opening the link, make sure to open the image in the tweet.

It is working as expected. Tested in latest Firefox.

The buttons appear only when an image is open (and when url contains 'photo')
For example : Install the script and open this link and wait for few seconds.

Re: @Korb:
This could also be an issue with Firefox Content Security Policy with respect to Tampermonkey. See open issue here.

I've made a few updates. Can you please update once and check again?