Having serious problems switching from eSIM / SIM replacement process

I signed up to Lebara on a SIM-only deal and chose to use eSIM.
Since then, I’ve been trying to sort out a SIM replacement / switch, but it has been an absolute nightmare. Customer service have not understood my issue properly, and the whole process has been very frustrating.
Here’s what happened:

1. The first replacement SIM I was sent did not appear to have a number linked to it, so when I tried to use it to replace my eSIM, the process would not let me continue.
2. The second replacement SIM was sent after that, but when I tried to switch from my eSIM to that physical SIM, the online authentication process kept crashing.

At this point I still don’t have a proper resolution, and I’ve found customer service to be very poor throughout.
Can someone from Lebara please explain:

• how to correctly switch between eSIM and physical SIM,
• why the replacement SIM was not properly linked the first time,
• and how I can get this resolved without the online authentication page crashing?

I’d really appreciate help from someone who understands the issue properly.
Thanks.