None of these addresses show any balance in the app, where as according to both mempool.space and blockchair.com they have a balance larger than zero.
Im connected via VPN, maybe this is an issue?
The problem is with blockchair API that is rate limiting your IP address.
This is the link that's being called:
https://api.blockchair.com/bitcoin/addresses/balances?addresses=1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa,12c6DSiU4Rq3P4ZxziKxzrL5LmMBrzjrJXIf you click it with the same IP, you should see the error message saying
Your IP address is temporary blacklisted due to exceeding usage of API resources.
You can go to settings window (F2 shortcut) and change the API used for updating balances.
to make it really useful for me, i wanted to ask you @Coding Enthusiast if there is also a possibility of a kind of message when a transaction (in-/output) takes place from a BTC address listed in the list
No because this tool doesn't keep an open/active connection. It has to be manually updated.
Some block explorers API services offer a WebSocket service that can track address(es) which can be added but I'm afraid they offer very limited rates to force people to purchase their subscription. Meaning it may be a wasted effort.
My plan is to implement Electrum protocol and then use it here as well. It could take some time since I'm stuck trying to finish other stuff in my Bitcoin.Net library.
it would also be interesting to know if there is a possibility to run this project via a telegram bot as well
I don't really know, sorry.