This is an accepted solution.
This is Lana from Shopify. I see you're looking to change your store currency so I wanted to help you out.
The currency settings are disabled automatically once you make your first sale. This is because the currency can be quite a sensitive change - for example, it can cause inaccuracies in past reports and some confusion with pricing if you were selling in USD and then you suddenly change to CAD, (as 1CAD does not equal 1USD etc.). This means that in order to make the change, you will need to contact our live support here, and we will be able to open the currency settings so that you can switch to a different currency. The reason that you will have to go through our live support for this is because we currently do not have the ability to access your account information from the Shopify Community.
Would you like to tell me a little bit more about why you have decided to switch the currency at this point? If it is a case where you are looking to sell in multiple currencies, you can still have the main currency changed with the steps that I outlined above - but also, if you are using the Shopify Payments gateway, you are eligible to add other currencies to sell in alongside. Please do note that selling in multiple currencies is only possible with the Shopify Payments gateway at the moment, so if you do have it enabled you can take a look at how to set it up here.
Let me know if you have any other questions here at all and I will be able to help you out.