Updating program on remote PC

Hi, sorry I haven't found answer in a search and am at my wits end going round in circles.  I help my old mum with her laptop using Teamviewer, but today we had to update to new version of Teamviewer (over the phone, me telling Mum what to do) because I couldn't connect using the old version , and to complete the install Teamviewer is asking (on her remote laptop) for an administrator username and password.  First, is this asking for the Windows Admin credentials (as Mum is only a user) or Teamviewer Admin credentials? It's a Teamviewer badged window apparently, but could still be asking for either thing. I have a Teamviewer password for my laptop and a different one for Mum's (it's been years since I set this all up), but neither of them works in this case and nor do my Windows credentials (I have an administrator account on her laptop). I don't have a 'username' anywhere for Teamviewer. Can someone please tell me exactly what information is required at this step, as 'flying blind' over the phone with an 84 year old is doing my head in! Any and all help most gratefully received, thank you