Manually add these to the remote site settings found in Salesforce Setup:
If the remote site setting already exists, confirm that your Salesforce instance (i.e. na1, na35, etc) has not changed by comparing what exists in the current setting with what is in your address bar. If it is different, please update the remote site setting instance with what is in the address bar.
This can occur when Salesforce Performs an Instance refresh: https://help.salesforce.com/articleView?id=Instance-Refresh-Maintenance-FAQ&language=en_US&type=1
Please Check: Salesforce Setup > Company information > "Instance" field to see if the remote site instance has changed.