It could be a number of reasons Andreas. Most if not all stemming from the BoM.
BoM
radar is normally updated in 10 minute increments except when they switch it to wind finding (Balloon release) or maitenance or the rat that runs the server needs feeding again. Who knows. They rarely if ever put up a notice to say why it isn't showing.
As to sat photos that also can be from a number of issues including a very poor quality image that they won't show and hence there is a long delay before the next one is put up.
In the end both problems are not from your end. Hitting F5 gives you something to do while you wait for it to be fixed or whatever.
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