When I type in the URL (in the LAN) to manage the Exchange 2013 server (used to work by the way) all I get is the OWA login screen. Without having access to the EAS/ECP system how can I fix this???

Hi 

Ensure your Admin Mailbox is moved to Exchange 2013 from previous version.

Also try with 

https://localhost/ecp?clientver=15 mostly it should work.
There is no ECP in Exchange 2013. It has only EAC and EMS.
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Regards, 
Sathish