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Copper BB
Brand new Today, M590A1 Retrograde Walnut . Out of box the pump moved back and the action lock lever depressed. Disengaged and moved pump forward. The action lever closed. Cannot open the bolt or move the pump back. Has anyone experienced the same? Thanks.
If you are trying to pull back on the fore end before ejecting, especially on a very new pump, it will resist opening the action. Have you tried pushing forward on the pump action (relaxing any tension) and trying again?
First RTFOM! ;) Then field strip as described in the OM. Then watch some videos on further disassembly and cleaning and do so. I think Jerry Miculek has a video or two on the subject. A 500 video will be near identical procedure.

I prefer to "ease-in" a new gun VS "breaking-in". Once apart, you clean the grit out of the bolt and receiver left over from manufacturing, IF necessary. Carefully file the sharp edges from the many stampings taking care not to file on the sear, extractor claws, etc. (ie: parts that are SUPPOSED to be sharp). Then lube moving parts as you reassemble. Once back together, cycle the action and pull the trigger about 100 times adding oil as necessary. Dummy rounds are handy to check (and practice) function of the gun before you use live ammo.

PS: I don't recommend disassembling the trigger group but DO remove it for inspection.
Late to the party , but the action is locked ready to fire as it should be, if empty point in a safe direction and press the trigger, or with your middle finger (holding the gun in a firing position) depress the action release. When running a pump (or any long gun) apply forward pressure on the fore end and hold gun back to the shoulder with the other, this will give a neutral balance to the gun, stop action from unintentional opening at firing, permit smooth operation of pump, stop shooter from shooting low left (if right handed) and list goes on.