Did you tried finder? Search with finder. Or go to Galaxy Store app and search for bixby. If it's installed, you can open app and set your voice command or if it's not then install it. I am from India and I don't know if the Nepal carrier services work differently which effect the device.
then it has issues. Try one thing, go to settings-search for Galaxy Store app-clear cache. Then restart your phone and try opening store again. If the problem persists, clear data of store app and re log in. if it still persists then you'll need expert help