Hi. welcome to JA.
Sorry for the delay replying. Took some searching to locate the solution for you.
Apparently this is the child safety lock that has engaged.
There should be a latch lever up under the handle that you need to push to one side or the other. You should then be able to open the door.
Please let me know if this is not the case.
Glad to hear that you got it open.
Thank you for the accept.