Could be caused by a number of factors - In my experience, it's good OBD11 hygiene to periodically clear the App cache on your tablet/mobile phone BEFORE you start OBD App. This forces a fresh install of the database in memory cache, which sometimes helps.
The other possible cause could be (and I'm guessing) a failure to enter the correct security code, the first time that you try. Not sure if you are aware, but the control modules in a mk7 get very cranky if the security code isn't entered correctly. There's a "mistake counter" in every module (which you can read) and if this counter is exceeded, the module spits-the-dummy. When this happens, the module will refuse to accept any more entries for a period of time - which is measured with the ignition turned-on. This lock-out time is variable, but about 10 minutes is normal. so, you may think that you have access, but error messages like the one that you posted can arise from these cases.
Don