Ответ:

1. We couldn't have a barbecue in the garden because it was raining.

2. Josh couldn't swim because the sea was very rough.

3. I couldn't go to school because I wasn't well.

4. Liam couldn't finish his burger because he was full.

5. We couldn't put up the tent because it was too windy.

6. Harriet couldn't sleep because she wasn't tired.