{"software":{"name":"LanguageTool","version":"3.9","buildDate":"2017-09-26 10:01","apiVersion":1,"status":""},"warnings":{"incompleteResults":false},"language":{"name":"English (US)","code":"en-US"},"matches":[{"message":"This sentence does not start with an uppercase letter","shortMessage":"","replacements":[{"value":"My"}],"offset":0,"length":2,"context":{"text":"my text","offset":0,"length":2},"rule":{"id":"UPPERCASE_SENTENCE_START","description":"Checks that a sentence starts with an uppercase letter","issueType":"typographical","category":{"id":"CASING","name":"Capitalization"}}}]}
I got it to work, but your wiki needs an update. There is no Options->Configure TexStudio->Grammar anymore. Now is Options->Configure TexStudio->Language Checking