Hard to say without knowing which method you used to install HomeAssistant.

But I never found mdns .local addresses to be very reliable. They work 80-90% of the time, but the remaining 10-20% are a hassle.

Instead I’d recommend you install PiHole (in a docker container is easiest). PiHole is a DNS server intended for network-level ad-blocking. But it also have a handy feature of defining local DNS entries, so you can have HomeAssistant.myhome or HomeAssistant.whatever (.local should not be used with PiHole local DNS because .local is meant for mdns)