Unable to connect to remote PCs following a change of phone supplier at remote site

I work on a voluntary unpaid basis for a Hospital Radio Station (Coastway Hospital Radio,Brighton) at which there are 4 PCs on a LAN which have free use of TeamViewer, and which I need to be able to contact from home. A few days ago Coastway's telephone line, which also carries broadband, was changed to a different supplier, but at the time the broadband was not replugged, meaning that the LAN was disconnected from the Internet for several hours. It has since been plugged in and the Internet is now working on all PCs, but TeamViewer isn't. All display the normal screen used for remote access, but when I try to  access any of them I get  the following message after a longish pause:- "No connection to partner. Partner did not connect to router. Error code: WaitForConnectFailed". At the same time the remote PC displays "Incoming connect", but the does nothing however long you wait. Can you advise?

Richard Davis