IMHO, you MUST get a ChargeplaceScotland RFID card. There are three reasons for this.
First, some of the remoter areas have patchy or nonexistent mobile coverage here in Scotland where the app doesn't connect and it can be impossible to phone the helpline (who are generally sympathetic, friendly and just as frustrated as you at that point - see below).
Secondly, some machines just don't seem to work with the app even with a conection.
Thirdly, and most important of all, over the last year or so, the CPS mobile app has been "upgraded" by the contractors, which translates as completely wrecked. It is now by a considerable margin the worst mobile app I have ever used for any purpose. Ever. Take a deep beath and read on...
It always opens by logging me out and saying it's sent me a verification code by email but one is never sent. It always defaults to my location being the centre of Edinburgh (160+ miles away from where I live) wherever I am, while every single Scottish charger is stated to be exactly 3983 miles from me, wherever they are. The charging status info hardly works (it says the charger's occupied when free, etc.). If you type anything other than very slowly in the search box it doesn't work. Graphics often show chargers but no underlying map is displayed so you can't see where they are; when it does display, the info sometimes doesn't match the charger. The buffering takes forever and frequently freezes. The screen mostly doesn't respond, so tapping a charger icon doesn't pop up the charger details.
It is the worst piece of software I've ever experienced - from a practical point of view it's completely unusable. Ironically the last two moves of the maintainance contract have been because of lousy performance by the contractors. But each subsequent one has been worse than the last - privatisation strikes again...
I'm not alone in this. If you want a (sort of) fun 20 minutes, go to the Play Store on your phone, search for the CPS app and read the reviews. There are 409 of them and the average score out of a possible 5 is just 1.1.