Get last value send from sensor

I have read all corresponding topic here bur did not get a solution and did lot of Google research
Following situation:
Weather station sending values every hours to Hass, deep sleep between, works fine
no I added a device with display somewhere to show some of these values.
But nothing is display until there is a new value from the weather station. Code seams OK as if I change the topic to one thats gets values every 10 seconds i.e. t he values are display.
I use the HA MQTT Broker to publish the values from the weather station to HA and to receive subscribed values on the new device.
Is there any possibility to get the last known value at once, when starting the displaying device?

thanks for any hep or hint

You need to get your weather station to set the retained flag on all messages it sends to the broker. You may also have to disable LWT (last will and testament).

Thanks a lot, will not be so easy I think, as I will have to reflash the weather stations ESP8266. As in case of deep sleep (solar powered) not OTA. So I have to disassemble my weather station totally to reflash. OK
Regards
Rainer