If you have mistakenly locked the camera of your browser and you are not able to take the photo of your Credit/Debit card, you would just need to allow access by following the below steps;

Click on the "Lock" which is located on the top left side of your browser on the left-hand side of the URL followed by Allow as shown below; 

Your last step would be to click on the "Reload" button and the page will refresh. 

That's it! You have unlocked your camera and you are able to complete the process.