Issue installing Xero app

I'm trialling out Akaunting on my self-hosted server.
It has been installed and appears to function correctly.
However, I cannot install the Xero app. When I click on it, it starts and hangs at 25% downloading.
Is there an issue specifically with the Xero app? I have tried other free apps and they all download and install without issues.

I think the inability to download was linked to the built-in firewall. I disabled the firewall in the .env file and downloading and installing the plugin then worked.

A further update: after installing the app, I realised it doesn't actually work. This might be because there's a comment about having the double-entry accounting app which I don't have. But it's not explicitly mentioned if this is a prerequisite to using the Xero app...

As a second option, I signed up for a trial on the cloud platform. First app I want to install is the Xero app. It doesn't install!

On my cloud platform, it goes up to 100% in the installation process and then just hangs there. I have tried other apps, they install OK.

As a trial user, it seems impossible to get any support - it's only available to people who have already purchased. The dedicated support is also a payable add-on.

It's a shame as this software looked like a nice alternative to Xero but having everything including support behind a paywall without any apparent support before buying during a trial period is a turn-off :(