Failed to connect to Nextcloud at <IP address>

Nextcloud version (eg, 10.0.2): Raspberry Pi 2 Western Digital box
Operating system and version (eg, Ubuntu 16.04):
Apache or nginx version (eg, Apache 2.4.25):
PHP version (eg, 5.6):
Is this the first time you’ve seen this error and can you replicate it?: Yes

The issue you are facing:

Using the Windows 10 System Tray utility:

"Failed t connect to Nextcloud at
Error downloading - server replied: Bad Request" is the correct address. Unfortunately, DHCP updated this address from the previous one - 192.168.2.x. The latter is inaccessible for obvious reasons. I can PuTTY to and confirm that this address represents the Nextcloud box.

What edit operations do I need to perform to restore the connectivity? The desktop client is unable to access the Nextcloud box too. There is nothing in this desktop app that will permit me to set the new IP address via the General or Network toolbar buttons. The Activity toolbar button displays a blank page.

As you can understand, I have no clue about PHP settings which is perhaps where the issue lies.

Thanks for your help.

Did you try https instead of http?

HTTPS is not enabled since this is purely an eval box. HTTP was working fine until the IP address changed. Somewhere the old IP address is interfering (having been logged in a PHP related file) with the access.