If you are using the Quotes and Exchange Rate extension, I would not be surprised if it stopped working. The source it uses, AlphaVantage, has been quite unreliable for quite a while and appears they have stopped supporting some Exchanges.
If you have been using Q & ER I would recommend de-installing it and using Quote Loader. QL has proven to be very reliable and has many more options.
The basic information on Quote Loader and pointers to the PDF file on its usage can be found at: