I would not recommend using the plugin to download historical data, other than to backfill the lookback period when starting a script. IGs limits for historical data is VERY low, which means you will easily exhaust your weekly limit. If you do, you will not even be able to start a script if even a single minute of data is missing.

That said, it should work with the download script, IF you stay within the time range given in the FAQ: https://labs.ig.com/faq.

My guess for the error message: You have tried to download data from today = Sunday. IG is not open until late in the evening on Sundays, so there are no ticks to be found within the range stated in the error message.

The second error is probably because you are trying to fetch data too far back in time, again refer to the FAQ.