Ring doorbell 3 Plus not ringing indoor chime nor getting power (despite electrician checking, and new mechanical unit!)

Recently my Ring doorbell stopped ringing my indoor mechanical 'ding dong’ chime AND receiving the trickle charge from it. It sounded as if my indoor chime/wiring had a problem. I ascertained from Ring that although the app says “hard wired” - that just meant it had wires connected (even if not powering the ring unit.) I was advised to check the wiring. I have had an electrician today to replace my whole indoor mechanical chime with transformer (model number D3230) that has been working well for 3 years. It was Friedland, which I ordered, Amazon.co.uk though now the name is badged Honeywell. The electrician replaced the mechanical chime with the new unit including transformer. He showed the power was going through the chime with a device. He took off the Ring doorbell outside, then showed my new mechanical indoor chime DID ding-dong when not using the Ring button, and then checked the wiring outside & reconnected to the Ring Unit. All through this I was going in the app to select the settings to tell the Ring to ring my indoor chime. Trying and trying and trying again. When he removed the Ring bell outside, my app did recognise the ring it wasn’t connected, so I went through the set up again, telling the app to work with & ring my indoor chime.) It didn’t. It was so simple to link with my indoor chime when I first bought this Ring bell, it’s not like I can’t follow app instructions. The ring is also not receiving power. Does anyone know why my Ring Bell suddenly won’t operate/charge from my mechanical chime? Is this a fault it could have? I know that I could get another Ring plug in chime, but please understand I only ever bought this Ring because it would activate the traditional chime (e.g. if the internet was down) and be powered by it i.e not worry about constantly removing & recharging a bettery! That is my main concern. Not only do I have a seemingly fault Ring unit, I’ve wasted money on a new indoor unit & an electrician changing the mechanical chime that maybe didn’t need changing. I’m a bit lost now.