Cant connect call, business phone keeps losing connections

It has not been possible to connect your call. Hi I am using a VOIP server to receive business calls. However I keep getting errors when calling such as it has not been possible to connect your call, even though the number works fine on my personal phone. Is it a problem with my VOIP, maybe their software is having problems. Can anyone advise if they have a business number and do they use VOIP? Thanks