Hi @HarryBrunning ,
I am not an expert in time series forecasting, but looking at the data and the decomposition plot, it seems that the dataset contains too much noise and the noise (random ups and downs) is making it really hard for the model to make future predictions. The forecasted number is simply the simple average across all month and seems like this is the best the model can do here.
I feel that the amount of gaps (imputed as 0s) are causing a big problem here! 16 zeros out of 46 observations, that's 35% of data missing.
You mentioned that you would expect to see seasonal effect (e.g. Dec being higher).
In the sample data, there are four observation for December: 2019-12-01: 0; 2020: 41.25; 2021: 30, 2022:30.
However, none of these Decembers were the highest in the year, and among the December month observations, there are big dispersions as well (ranging from 0 - 41.25).
Intuitively, if you had give this data to a human expert, he/she probably wouldn't be able to come up with a good prediction, simply due to the noise in the data.