Most likely, your lens is too close to the subject. The Nikon 55-300mm has a minimum focusing distance of about 1.4 m (4.5 ft), so it cannot autofocus on anything closer than that.

Indoor light can also make autofocus struggle, especially with a telephoto zoom. That’s separate from aperture or ISO directly causing the issue, though low light does make focusing harder.

Your D3300 also uses focus-priority by default, which means it may refuse to fire the shutter until focus is confirmed. That explains why it shoots in manual focus mode even when autofocus won’t lock.

What to try:

• Move farther from the subject.
• Zoom wider if possible and give the lens more light.
• Use manual focus if needed.
• If you just want the shutter to fire, look into release-priority mode, but expect more out-of-focus shots.
• Stopping down the aperture can increase depth of field, which may help subjects appear more in focus, but it won’t bypass the lens’s minimum focus distance.

If you want to photograph nearby subjects indoors, this lens may simply not be the best choice for that use.