Step 1: Go to Gmail on Chromebook or PC.

Step 2: Click the Show Search Options icon thst is depicted below.

Step 3: Type the email or domain name (@.......) into the From dialog box. The email or domain name would be on the emails that is being blocked and sent to spam. 

Step 4: Then click Create filter

Step 6: Check the Never send it to Spam box

Step 7: Check the Categorize as: box and change it to Primary

Step 8: Click Create filter.

Note: filter will not be applied to old conversations in Spam or Trash