Hey @gabino.alonso there is actually nothing you can do about it.
The problem here is, that you have time axis and each record is given as datetime. So what plotly does is that it shows your data as is, e.g. each record at the given time. If there is no record, there is no bar shown BUT the space on the axis is reserved.
What you will have to do is, prepare your data so that you have monthly records. How you do this depends on your goals- you could do a monthly mean- value or any other operation.
I answered quite often to these kind of questions, you could search the forum using “@aimped barplot” or similar.
Unfortunately in some cases I can group weekly, monthly or yearly (like in the example I posted above) but in others I would like to be able to show the individual data.
The only way I see is converting the time axis to categorical. You won’t have gaps but the graph might be harder to read due to missing time continuity.