WP Unable to install any app on lumia phone

[nRiTeCh]

I'm very furious on this.
I have downloaded some useful apps for my sisters lumia 730 from windows app store via pc.
The files are in extension .xap.

When I copy them to the phone and try to install I get this error for all the files tried to install:

Can't install company app. There's a problem with this company app. Contact your company's person for help.

What is the issue and how it can be resolved?

 

[smnrock]

^ I guess you should install directly in the phone from the store...not by downloading from PC and copying to phone.

I could be wrong, but what you are trying to do is called sideloading and it's possible only on developer unlocked phones.

 

[redhatperl]

Yup, even with developer unlock using traditional methods you can only get 5 apps for side loading.

 

[nRiTeCh]

I think you are right. I activated internet on phone and downloaded the same apps and they got installed without any issues.
Strange!! But people are able to sideload apps as well in their phones else why would have MS given the option Download and install manually on their windowsphone store??