My first attempt at using DMC (Dell Mobile Connect) Windows 10 and iPhone 12 went reasonably well. It connected, I could see files and contacts, could send a text (but wasn't notified of receiving any), notifications appeared on the PC - but I could make phone calls (it said it wasn't connected - even though elsehere it said it was - and obviously was).

Next day, I cannot connect either by scanning the QR code or by "using a code". In both cases, my phone says "Unable to connect. Please check your network connection & try again". My phone and PC both have high speed network access. I have re-started the phone and the PC has been re-booted.