can you share which plugin you are installing , if its the package you download from themeforest then please not that you have to unzip the package first inside the zip file you will find folder wplms 4.9 which you need to install in wp-admin -> themes -> add new.
Unpacking the package…
Installing the plugin…
The package could not be installed. No valid plugins were found.
Plugin installation failed.
Go to Plugin Installer
can you share which plugin you are installing , if its the package you download from themeforest then please not that you have to unzip the package first inside the zip file you will find folder wplms 4.9 which you need to install in wp-admin -> themes -> add new.