SMC.EXE which stops & starts the Symantec client console is not defined in any path, therefore Windows will not find it if you try to run it from a Command Prompt or remotely as in your command.
Windows will run the command from the Run... box because it is a 'known' application as defined in this Registry key. Note the the entry below is a folder / key named Smc.exe with a default value pointing to the actual exe.
HKEY_LOCAL_MACHINE\SOFT WARE\Microsoft\Windows\CurrentVersion\App Paths\Smc.exe
To fix your conundrum, this would be the command you need to run: (Note the PSEXEC & watch out for 64bit machines)
c:\PsTools>psexec.exe \\computer_IP -u [username] -p [password] "C:\Program Files\Symantec\Symantec Endpoint Protection\smc.exe" -stop
c:\PsTools>psexec.exe \\computer_IP -u [username] -p [password] "C:\Program Files\Symantec\Symantec Endpoint Protection\smc.exe" -start
Alternatively, if you really wanted to work with the services, you could use the built in SC.EXE from Microsoft that controls services. Your commands would look similar to this:
sc.exe \\computername_or_IP stop "Symantec Antivirus"
sc.exe \\computername_or_IP stop "ccEvtMgr"
sc.exe \\computername_or_IP stop "SmcService"
sc.exe \\computername_or_IP stop "SNAC"
sc.exe \\computername_or_IP stop "ccSetMgr"
& remember to start your services again.