[TANYA] instal themes/plugin lama dan klik setting>>permalink server error

Mohon bantuannya,
Saya mencoba menginstal themes ataupun plugin, tapi tidak pernah berhasil.
Hanya ada tulisan “unpacking the package……” dan laaamaaaa. Ujung-ujungnya tidak berhasil.

Lalu saat klik setting -> permalinks, muncul keterangan :

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@wanitaproduktif.biz and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

tambahan informasi,Koneksi internet lancar.

Mohon masukannya. Terima kasih.