I was renting to a business for over 14 years. The business was sold. The new owners negotiated a new lease, but never signed the lease and moved the business after paying the lowered rent for 5 months. When they moved, they left all the store fixtures (display cases, computer, garbage), and only took merchandise. I gave them a 10 day notice to quit the day they moved out. That gave them until the end of the month. They have not paid the rent for the next month. They gave me a key 13 days after they moved out. Can I take possession and change the locks? Who owns what they left?
The new owners were leasing from month to month. When they moved out you had the right to take possession immediately. If there was any doubt, the matter was clarified when they handed you the key.
It appears that they abandoned everything left in the store after delivering the key. This stuff appears to have little value (except possibly the computer). Move the property off premises and give them 30 days to claim it, provided they pay a reasonable storage charge. Tell them that you will dispose of the property after that time. Send the notice certified and keep a copy.