Smart Meter - electricity graph no longer shows two tarifs

[peterk]

The graphs for the electricity device of my P1 Smart Meter hardware used to show the high and low rates as usage_1 and usage_2, with different colors (light and darker blue) to distuinguish between both rates.
It also showed the words "Usage_1" and "Usage_2" in the legend below the graph.

Since 2 days this has suddenly disappeared in the "Last 7 Days" graph (the uppermost graph on the page).
The entire line now has the same color.
Also, the legend below the graph now shows only the single word "Usage".

The Last Week bar-graph, however, still shows the stacked bar with different colors for high and low tarif and both "Usage_1" and "Usage_2" in its legend.

The Smart Meter is still delivering the same data format as before, which still contains current usage and counter values for tarif 1 and 2.

Any explanation? Any suggestion how I can fix this?
Restarting or rebooting doesn't help.