This should work. Please check which version of ServiceConnection_Facebook,OAuth,OAuthSIgning paclets are being used.
Ideally it should be:
In[1]:= PacletInformation["ServiceConnection_Facebook"]
Out[1]= {"Name" -> "ServiceConnection_Facebook",
"Version" -> "11.1.12", "BuildNumber" -> "", "Qualifier" -> "",
"WolframVersion" -> "11+", "SystemID" -> All, "Description" -> "",
"Category" -> "", "Creator" -> "", "Publisher" -> "",
"Support" -> "", "Internal" -> False,
"Location" ->
"C:\\Users\\damanjits\\AppData\\Roaming\\Mathematica\\Paclets\\\
Repository\\ServiceConnection_Facebook-11.1.12",
"Context" -> {"Facebook`", "FacebookLoad`"}, "Enabled" -> True,
"Loading" -> Manual}
In[2]:= $Version
Out[2]= "11.1.0 for Microsoft Windows (64-bit) (March 13, 2017)"
In[3]:= facebook = ServiceConnect["Facebook"]
Out[3]= ServiceObject["Facebook",
"ID" -> "connection-a561cb52c34c33b0a72908df611cb7d9"]
In[4]:= facebook["Cover"] // Head
Out[4]= Image
In[5]:= PacletInformation["OAuth"]
Out[5]= {"Name" -> "OAuth", "Version" -> "11.1.48",
"BuildNumber" -> "", "Qualifier" -> "", "WolframVersion" -> "11.0+",
"SystemID" -> All, "Description" -> "", "Category" -> "",
"Creator" -> "", "Publisher" -> "", "Support" -> "",
"Internal" -> False,
"Location" ->
"C:\\Users\\damanjits\\AppData\\Roaming\\Mathematica\\Paclets\\\
Repository\\OAuth-11.1.48", "Context" -> {"OAuthLoader`", "OAuth`"},
"Enabled" -> True, "Loading" -> Automatic}
In[6]:= PacletInformation["OAuthSigning"]
Out[6]= {"Name" -> "OAuthSigning", "Version" -> "11.1.0",
"BuildNumber" -> "", "Qualifier" -> "", "WolframVersion" -> "10.4+",
"SystemID" -> All, "Description" -> "", "Category" -> "",
"Creator" -> "", "Publisher" -> "", "Support" -> "",
"Internal" -> False,
"Location" ->
"C:\\Program Files\\Wolfram \
Research\\Mathematica\\11.1\\SystemFiles\\Links\\OAuthSigning",
"Context" -> {"OAuthSigning`"}, "Enabled" -> True,
"Loading" -> Manual}
You can also try deleting OAuth and ServiceConnection_Facebook directories from FileNameJoin[{$UserBaseDirectory, "Paclets", "Repository"}]
and try connecting to Facebook service again.