Help! Can't activate sim

I got a simple phone for my 83 year old neighbour, paid for the first month with Lebara to get her going, now I have the phone & even though the sim is in it it says "no sim" presumably it needs activating.
"Download the MyLebara app" says the letter. Download onto what? Can't be the new phone, that hasn't been activated yet. So I tried on my computer - and it wants to download to the only option, MY phone! I don't want it on my phone. I tried ringing customer services, very hard to hear the operator, I don't think he understood my question as he cut me off.
On the website it says something like - pop in the sim & you're good to go - but I can't activate it. Surely everyone has to get their first device, you can't always have one to set up the second?

NiceCupofTea the SIM should activate when inserted into an unlocked phone and turned on. If the phone is displaying 'no SIM' when turned on indicates there is an issue with the SIM of the phone. Are you able to test the SIM in another phone to determine which side the issue is on?

Martin I have had the phone checked out & it seems not to be working, some problem with the sim reader. I have also had an email from Lebara telling me I have a limited time to activate it. It's a gift for a very elderly lady so she can have free phone calls, but it looks like I'm going to have to buy her another one. Just hope I can get it sorted before the time runs out.

NiceCupofTea good to hear that you've discovered the cause of the issue. What you could do is activate the SIM in a different handset and then just pop it in a draw until you have the new handset for your neighbour. Please do let me know how this one goes.

Yes, that is what I tried to do, but I don't have access to another phone that takes the full sized SIM, the helpful lady at the shop tried a different SIM in it and it didn't work. Most new phones seem to take the mini SIM.

NiceCupofTea Yes I don't think I've had to use a large SIM for a good few years now!

I have bought another phone, it should be arriving today, thinking the phone is faulty - but my husband suddenly thought, these phones are on the 2G network. My husband has one, had loads of messages stating "3G is being turned off" but was told the phone will be fine as it's on 2G. His phone is fine.
Is that the problem? I need a low cost solution to getting my neighbour a phone, hence Lebara! I think having now bought her 2 phones (& a Sim) it is not turning out to be low cost.