The MSDTC transaction manager failing : It was unable to pull the transaction from the source transaction manager due to communication problems

Microsoft Tech Gurus,
Can you please assist on this issue. ? There are 3 different errors stacks for this issue - Our Application is not connecting with MS SQL Server. Everything was fine until Monday. There are changes have done on those Apps and DB servers.
Please refer the attached document - which has all the errors with details. Appreciate all your support.!
Error 1 :
TISAppenderLog4net.Log4NetException: The underlying provider failed on Open. ---> System.Data.EntityException: The underlying provider failed on Open. ---> System.Transactions.TransactionManagerCommunicationException: Communication with the underlying transaction manager has failed. ---> System.Runtime.InteropServices.COMException: The MSDTC transaction manager was unable to pull the transaction from the source transaction manager due to communication problems. Possible causes are: a firewall is present and it doesn't have ...