Hello,
It could be 3 reasons of the problem:
1) You did not activate theme using the purchase code
2) Conflict with some third-party plugin that you also installed that change the link to the plugins installation page. Do you have access to Appearance > Install Plugins?
3) Your user has limited permissions
If it does not help provide me temporary Dashboard and FTP access to your site to check.
Also, you can download required plugins from this page https://www.8theme.com/downloads/ and install them manually.
Regards