The system might show $0 if it hasn’t finished calculating everything. You will see a pop-up window in the left corner that will disappear when the calculations are finished.
Your account could have $0 in gains/income/costs if you only had purchases during the tax year and no disposals.
Your account will stop updating if you have exceeded the total number of transactions allowed by your plan. For Free accounts, the calculations will stop if you have more than 10k transactions.
If none of this applies and you are still having issues with this then please send us a message via Live chat or email so we could have a closer look.