Your Walmart account can become disconnected from Sellbrite for a several reasons.
Sometimes there can be a failure within Walmart's API, which will cause Walmart to become disconnected. If this is the case, reconnecting is easy.
Navigate to Settings > Sales Channel Integrations, then select Walmart to get to your Walmart Channel Settings. From here, simply click "Reconnect".
If this does not reconnect your Walmart account, check your Walmart permissions to confirm that you have granted Sellbrite full access to your account.
Navigate to https://developer.walmart.com/#/delegateAccess
Make sure that all of the permissions for Sellbrite are set to "Full Access." They should match the screenshot below exactly.
Next, you will need to generate new API keys. These are your Client ID and Client Secret. If you already have these in the Walmart Channel Settings page in Sellbrite, you may need to generate new ones. You can do this by clicking "Reset".
Once you have generated new API keys, you will need to copy them.
Navigate back to the Walmart Channel Settings page in Sellbrite, and paste API keys in the Walmart Client ID field, and Walmart Client Secret field. Now click "Reconnect."
NOTE: Even after you have successfully reconnected your account, Walmart can take up to 5 days to acknowledge and accept the connection request from Sellbrite, but typically it will connect much sooner (as soon as a few minutes).