TPO requires tick data. This indicator in MultiCharts shows that there is some data that was loaded, but not yet processed (plotted in MultiCharts). That is possible that there is not enough PC processing power to process the data without putting it into a queue.
How different is the data processing when plotting volume profile and the TPO study?
Both use tick data and with volume profile I never received a red sign.
The difference is in the data requests and in the data processing. TPO requests rough 1 tick data, indicator processes the data and plots the results on the chart. While Volume Profile requests Volume Delta resolution, that is being formed by the TsServer.