You expected the walk to tire your dog out. Instead they pace around the room, grab a toy, then bark at the window. They may still need something, or they may have had more noise, excitement, and close encounters than they could comfortably process. A longer walk is not always the answer.
First, check for physical problems. Heavy panting that does not settle, limping, pain, overheating, or a sudden change in behavior calls for veterinary advice. Make sure your dog has water and a comfortable place to rest. Don't label persistent agitation a training failure while a health issue is possible.
Look at the walk you just had
Was it full of traffic, dogs, or strangers? Did your dog pull through several difficult passes? Try a shorter, quieter route next time with more chances to sniff and fewer forced greetings. Some dogs come home calmer after a gentle twenty minutes than after an intense hour.
Once home, offer a predictable wind-down: water, a quiet resting space, and a safe activity such as a food puzzle or chew if your dog enjoys one. Don't require a long down-stay from a dog who is still too worked up to settle. Reward them for choosing their bed when they relax. Keep a simple record of which walks end calmly and which do not, the pattern can guide changes.
If restlessness persists, worsens, or happens even after easy days, talk with your veterinarian and a qualified, reward-based behavior professional. Your dog may need a different balance of activity and rest, not simply more mileage.
Sources: Dogs Trust: Helping a hyper or restless dog to calm down. Dogs Trust: Reactive dogs - why it happens and how to help.