Lightning: can't deposit btc

Hi all,

I never used Lightning before and I am struggling to deposit funds on a Lightning wallet I just created.

Each time I am trying to withdraw btc from Kraken to my new Lightning wallet created, the funds don't arrive on Lightning and are automatically returned to my Kraken account.

Basically, I created a new wallet on Phoenix (iOS), generated a Lightning invoice in the app, and used it as "destination address" on Kraken (Lightning network is selected on Kraken). Kraken accepts the withdrawal and marks it as "pending". However, after a couple of minutes, the funds are back on my Kraken account - they never appeared on my Phoenix wallet.

I also tried with Wallet of Satoshi and Muun wallets and I have the exact same problem.

I tried to find people experiencing the same, watched Youtube videos about how to use Lightning etc. but I could not find any relevant information for my problem.

What am I doing wrong here?

Thanks for your help!