Problem in accessing Navision Financial using Citrix

We are retail company and our stores are using Navision Financial by citrix server located in HO. We have enough user licences for citrix server. But from last few days some of our stores can not access Navision via Citrix. Not any setup was changed. Some stores can still access Citrix, its not completely down. Anybody has such experiance and resolution then please help me.

You have enough user license for citrix, but do you have for Navision?
There is any error message?

We have enough licences for Navision also.

It is trying to connect citrix and then giving following error and coming out:


Navision

Closing the Citrix ICA client window will disconnect you from the Citrix Presentation Server.

Are you sure you want to close and disconnect?

OK Cancel