Import .json from computer

That style of report transformation has been depreciated from NG Software. If you have used it to develop your own Report transformation, you will need to use older versions of Manager, see Restoring data issue - #2 by Patch

If you have just used the Report transformations distributed by NG Software then using the renamed current ones would be sensible. See Report Transformations - No-code development platform for details of the new approach.