Chain came off and brake won't reset - Ryobi 18-inch Electric Chainsaw Chain Saws

this seems to be a chain brake that's applied , try turning off chain brake by pulling back on hand guard till a click is felt

some folks moving up from an older saw to a more modern saw are not so familiar with chain brakes and don't understand them and how they work

Chain adjusted too tight?
Chain Brake loaded with saw dust?

There will be a chain brake, grab the brake handle and pull it firmly back to the top handle, this should didd engage the brake, if the chain has de railed the drive lonks will have burs on them which will make it tight in the bar, you need to file all these burs off.

Sounds like the chain brake was set when you took the cover off. You need to disengage the chain brake (release it) so the round spindle will fit inside. Look for the two parts (one on cover, one on saw) that match up at the base of the chain brake. You won't be able to fit the whole cover on, but if you can line up where the metal triangular gear engages the chain brake, you can give it a snap to disengage it. What I have done in the past is to line up the two parts and push down on the top of the cover where they meet so as much of the gear is in the chain brake release as possible ( I put a knee on it ) and then give a snap to release it. Be careful though, because the cover part is plastic and you don't want to strip that part of the chain brake assembly. Good luck.

This sounds loke the chainbrake has activated, grab the hand guard and pull it fimly fully back to the top handle until it clicks and the brake is of, now try again.

Do you mean the chain won't move, or you can't get the blade off? The chain brake must be off to allow the chain to move. The chain brake handle has a housing that engages a gear attached to the chain brake inside the cover where the blade is attached. The brake must be off to remove the cover (usually held on by two nuts). The blade tension screw should be loosened to allow the blade to be removed, then retightened when replacing the blade. Tightening it pushes the blade out from the saw, so if it is tight, you won't be able to remove the blade. Hope this helps.

Sounds like the chain brake is on, grab the hand guard and pull it firmly back to the top handle to release the brake.

The chain brake is activated, pull the hand guard fully back to the top handle until you hear the click of the brake loading

The chain brake is tripped. try this:
Reset Chain Brake by Dolfoff
Please follow this link, http://www.fixya.com/support/t3102817-re_install_side_cover_after_chain
cursor down to “Best Solution”, while there click the “Was this helpful? [Yes]” button
If you don’t have a vise a large C clamp to a work surface might work, you may still need a block or two of wood. HTH
Lou
It takes considerable force to reset the brake. I should click when it nests in the detent. If you are unable to reset it try your local chainsaw seller/mechanic, probably free. A spare chain purchase would be a nice "Thank You" HTH
Lou

Either the chain brake is on or the chain is too tight To reset chain brake pull the guard hard back toward the handle and I mean hard! They have a really strong spring and you should hear a "clack" when it resets Hope this helps