If you're seeing a sudden drop off in clicks and commissions for an advertiser with a Refersion account this may be due to their Refersion reporting limits.
The advertiser/brand may have a limit on the number of reports Refersion allows them to run. Once the limit is reached the API will no longer return data.
Please check with whoever set up the account either from the brand or Refersion. If this is the case it is not an error with Affluent or the API, the reporting limit needs to be increased so that the API returns data.