My single side regulator is going bad. When I turn the gas on I hear gas or air coming out. My stove still works but this makes me nervous. I disconnected the gas line from the tank and switched the lever on the other side to run that tank. When I turned the valve on and then the stove I got a very low flame for a minute then it went out. My question is do I need both tanks connected and on for the gas to work? I also am having a hard time finding a regulator the same size.

We had our red regulator on the door side leak and fail a few years ago. Replaced with another Marshall regulator. Marshall Excelsior MEGR-130-30 High Pressure Regulator or you could probably use a JR Products 07-30325 instead. You should be able to use LP with only one tank connected and the change over pointed in the correct direction. Don't open the tank valve too quickly or the OPD ( over fill protection device) valve might see it as a leak and shut the supply down. I would turn the good side tank to off. Slowly release the pressure loosening the fitting to the tank to relieve pressure. Reconnect the fitting to the pigtail and slowly reopen the tank valve. Then test for lp by opening and lighting burners on your LP range.

I helped our friend replace the curbside regulator on his Redwood when it failed, I also got a replacement, it hasn't failed yet (one of Murphy's laws must be "if you have a spare you won't need it"). I would be careful running propane with that leak, not sure if the flow from the good tank will go back to the bad regulator when the tank switches over when it goes empty, I know in cooler weather propane is left in the tank after the switch over.
If replacing the regulator yourself, be sure to use Teflon tape for propane on the fittings, not the white stuff.

When the cheap Chinese curbside regulator on mine crapped out the cheap Chinese changeover seemed to quit at the same time so replaced both with Marshall brand regulators found at the local rv parts shop, also could be found at your local LP dealer.

My single side regulator is going bad. When I turn the gas on I hear gas or air coming out. My stove still works but this makes me nervous. I disconnected the gas line from the tank and switched the lever on the other side to run that tank. When I turned the valve on and then the stove I got a very low flame for a minute then it went out. My question is do I need both tanks connected and on for the gas to work? I also am having a hard time finding a regulator the same size.

Here is a link to the same regulator:
https://www.amazon.com/gp/product/B007HRWL4C/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Here is a link to the one I replaced mine:
https://www.amazon.com/gp/product/B00HSMMAEC/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Here is a link to the changeover regulator that I used to replace mine:
https://www.amazon.com/gp/product/B004A2WUBG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

In the first 4 years of ownership, I had to replace both regulators and both pigtails due to them become leaky. Here is a link to the pigtails I used:
https://www.amazon.com/gp/product/B00FFAZE2O/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

I haven't any issues with the the regulators or pigtails since then.

Hope this helps.