Hi Cedric
This problem is not systematic, it appears sometimes, it's not a problem of service.
To show alert, you need to write in weewx.conf
show_last_updated_alert = 1
and forecasts
# Forecast defaults
forecast_enabled = 1
forecast_provider = aeris
forecast_api_id = xxxxxxxxxxxxxxxxxx
forecast_api_secret = yyyyyyyyyyyyyyyy
forecast_units = ca
forecast_interval_hours = 0 # values are 0,1,3 or 24
forecast_lang = fr
forecast_stale = 3540
forecast_aeris_use_metar = 1
forecast_alert_enabled = 1
forecast_alert_limit = 5
forecast_show_daily_forecast_link = 0
forecast_daily_forecast_link = ""
With xxxxxxxxxxxx and yyyyyyyyyyyyy your api identifier and "password" for aeris forecasts