what error are you getting? not working is a pretty wide net to cast.
do you get an error stating the database needs to be set to trustworthy?
is the new server 2012/14, and the "working servers" are 2008R2 or less? 2012 and above are using the 4.0 framework, and not 2.0, and that might affect your process.
otherwise, if the same code is working on another server, it's probably either permissions or web access.
the service account that is running SQL server matters. compare what domain account is used to run the service on the working servers vs this server.
does the CLR use a web service call to get the RTF conversion, or does it use windows.forms?
if it uses Windows.Forms,did you also register Windows.Forms, and then your CLR?
--Create assembly [System.Windows.Forms]
CREATE ASSEMBLY [System.Windows.Forms] AUTHORIZATION dbo
FROM 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Windows.Forms.dll'
WITH PERMISSION_SET = UNSAFE
GO
Lowell