I have a problem with the template tile under wearos in the companion app.
I have connected my galaxy watch 4 to it and except of the tempate tile it works ok.
But if i enter anything into the template tile content field it always displays: “error rendering template”.
Even if i enter a single charakter, this error message appears right away…
What am i doing wrong?
Just created an account for this as I was also looking for this exact issue at the moment. 
I have the same issue. Also with the Galaxy Watch 4 and just the template tile not working.
So far nothing worked to resolve this.
There seems to be a weird bug…
it did not work as i stated above…one hour later i opened the app on the phone again and navigated to the template tile input field and everything worked suddenly
i also saw the contents on the watch
i was so happy
a few hours later i went again to the input field in the app to modify the content slightly and as soon as i opened it the error message was displayed again (i did not change anything yet) and the tile is not working again, the watch also dispayes the error message… 
Hi Airwolf,
can you check if you have proper Bluetooth connection between your watch and phone? Mine is showing on both the watch and phone that they are connected through Bluetooth. But the watch does also state it is disconnected from the phone.
When opening the Wear App on my phone it also closes after a second or so showing me a black screen. I got the Wear app working with my headphones, but when I try to switch to the Galaxy watch within the Wear App it closes again.
connection is there and working.
All the other home assistant tiles are also working properly
I found a solution for my problem. There seems to be a bug with the Samsung Wear App. This really good post solved the issue for me: Solved: Wearable app is stuck on loading screen or crashes... - Samsung Community - 2769289
if you guys have “error rendering template” from the phone app then please check companion app logs for an error, tehre is probably some other error going on
Settings > companion app > troubleshooting > show and share logs
I was having the same issue. For me, the issue lies in my watch aggressively disconnecting from wifi (anytime it’s connected by bluetooth to my phone).
If I turn off bluetooth on my phone, the template will refresh / show data correctly.
Ideally, a data refresh request from the template would ask the watch to briefly connect to wifi.
the app does not handle those requests, its up to the watch how it works. You want to use a URL that will work both locally and remotely with wear OS as there is no URL switching. Watches simply dont stay connected long enough and tile refreshes do not request WiFi, they request whatever connection is available at the time.
Thank you for the feedback. The url for my home assistant server is accessible both internally and externally. My HA Companion version is 2023-12-4-11898. My wear OS version is 4.0 with an Android patch level of December 1, 2023.
Even though everything appears to be up to date, the HA Companion will not even show available entities unless I disable bluetooth on my phone. The weather complication on my watch does show regular updates, so it looks like the watch is connecting properly for that - just not for the HA Companion app. Looking through app permissions on the watch, I don’t see any permission that the weather app has that the HA Companion app does not have. Somehow the weather app is able to talk to it’s server any time, but the HA Companion app will only do it when there is not a Bluetooth connection to my phone.
Don’t know if this makes a difference or not, but my watch does not have a cellular connection.
yes thats a known issue for some users as its related to proxy stuff that Wear OS does.
you need to enable NAT loopback on your router as there is not much the app can do here. Yes other features may work but the issue is that your watch is trying to send/receive data home and the server is not recognizing it because its not being routed as your network expects.