language tool and texstudio won't work...

Hi! I have a problem getting languagetool v5.1 to work with texstudio 2.12.22 on Ubuntu 20.04.1. I followed the instructions and everything seems to work. The languge tool logo shows up at the lower end on texstudio window. When I check in the browser at http://localhost:8081/v2/check?language=en-US&text=my+text I get a json response that looks like this:

{"software":{"name":"LanguageTool","version":"5.1","buildDate":"2020-09-25 13:26","apiVersion":1,"premium":false,"premiumHint":"You might be missing errors only the Premium version can find. Contact us at support<at>languagetoolplus.com.","status":""},"warnings":{"incompleteResults":false},"language":{"name":"English (US)","code":"en-US","detectedLanguage":{"name":"English (US)","code":"en-US","confidence":0.65618557}},"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},"sentence":"my text","type":{"typeName":"Other"},"rule":{"id":"UPPERCASE_SENTENCE_START","description":"Checks that a sentence starts with an uppercase letter","issueType":"typographical","category":{"id":"CASING","name":"Capitalization"}},"ignoreForIncompleteSentence":true,"contextForSureMatch":-1}]}

this looks fine to me.
Also, grammar checking is enabled in the texstudio options. Language is set to en_US.
I don’t understand what is going on. Thanks for your help!

The LT result looks fine, so this might be an issue that the TeXstudio community can help with.