Make sure that your default picture app (see Default App Manager) is actually on the phone. You might have deleted it and are using a different app, but failed to make the new one the default.
Welcome to Android Central! You need to give more details. Which phone? What do you mean by "load photos and videos"? Are you trying to download them from a site? Or from your cloud storage? Or are you trying to upload them? Or are you talking about photos and videos sent via text messages?