Such issue is usually caused by unstable network connection. Make sure that your network connection is stable. If the error continues, please try the steps below to delete your cache information.

In Chrome

On your computer, open Chrome.

At the top right, click More More.

Click More tools and then Clear browsing data.

At the top, choose a time range. To delete everything, select Alal time.

Next to "Cookies and other site data" and "Cached images and files," check the boxes.

Click Clear data.

If you are on Firefox, try the steps below.

Click the menu button and select Settings.

1) Select the Privacy & Security panel.

2) In the Cookies and Site Data section, click Clear Data….

The video / ad bonus is not loading.

Many ads may not be available to you if you have not allowed personalized ads.

Please check your personalized ads settings.

Go to 

Facebook settings >Ads > Ad Settings

1. Then tap on 'Data about your activity from partners' option.

2. Toggle the option on and see if you get your ads back.

If you have already turned on the option, that means there are no ads available at the moment.

The ads may not load when there is no ad available to watch.