Connection Refused, But Worked A Few Minutes Ago

I am 100% brand new to all of this, but I bought and successfully set up a Raspberry Pi 4 and have been able to consistently access HA (after I replaced the first SD card, which was corrupted.) Now, suddenly, I am getting ERR_CONNECTION_REFUSED on any attempt to access the device through browser or PuTTY. I restarted my router (UniFi Dream Machine Pro) and I restarted the RP… both a few times, in fact. I’ve read through everything I can find here and so far have not found a solution that worked. Can anyone offer suggestions? My next step would be to reflash the SD card with a new HA image, I guess?

can you PING it

hate to say it SD card again

Thanks for the reply! I had other reasons to suspect the RP was bad, so I replaced it, and as of now I’m back to the old problem of no z-wave network starting… but HA is working just fine! Haha