Looking on the internet deeply has found these results:

conversion is not available is the most popular phrase on the web.

conversion is not supported 12,540 results on the web	conversion is not available 12,870 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
OLE DB provider "MSDASQL" for linked server "MYSQL" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ... Sep 24, 2014 ... OLE DB provider "MSDASQL" for linked server "SIMBA" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ... OLE DB provider "MSDASQL" for linked server "LinkServer" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ... OLE DB provider "MSDASQL" for linked server "LOCAL" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ...	If the wanted conversion is not available, the iconv_open function returns (iconv_t ) "Sybase connection warning: 2401, Level 11, state2: Character set conversion is not available between client character set 'ISO_1' and Server character set ... The requested conversion is not available. wFromType or wToType was not a valid type for the provider, and the provider was a version 2.0 or later provider. Message text. Character set conversion is not available between client character set '%.s' and server character set '%.s'. 1 . In this case the global variable errno can have the following values:.

conversion is not supported

12,540 results on the web

conversion is not available

12,870 results on the web

More popular!

OLE DB provider "MSDASQL" for linked server "MYSQL" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ...
Sep 24, 2014 ... OLE DB provider "MSDASQL" for linked server "SIMBA" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ...
OLE DB provider "MSDASQL" for linked server "LinkServer" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ...
OLE DB provider "MSDASQL" for linked server "LOCAL" returned message " Requested conversion is not supported.". Msg 7341, Level 16, ...

If the wanted conversion is not available, the iconv_open function returns (iconv_t )
"Sybase connection warning: 2401, Level 11, state2: Character set conversion is not available between client character set 'ISO_1' and Server character set ...
The requested conversion is not available. wFromType or wToType was not a valid type for the provider, and the provider was a version 2.0 or later provider.
Message text. Character set conversion is not available between client character set '%.*s' and server character set '%.*s'.
1 . In this case the global variable errno can have the following values:.