Yasin,
Sorry that you are seeing this issue. We have a known issue with CodeMix on Eclipse 2021 packages. The Extensions will not be installed or loaded.
The dev team is looking into it. Please downgrade to Eclipse 2020-09, install CodeMix and apply this patch.
Please note that CodeMix has reached its end of life and no new releases will be made. MyEclipse 2021 is the alternative which is based on Language Server tech.
We have a free trial of 30 days where you can evaluate it. If it suits your requirements, then you can convert your existing CodeMix license to MyEclipse license.
Apologies for inconvenience caused. Please let us know if you have any further questions.
–Swapna
Genuitec Support