I'd be happy to guide you on how to resubscribe and downgrade your plan.
You'll need first to login to your QuickBooks Online (QBO) trial expired account to select your plan. However, if the Downgrade your plan option on the Billing & Subscription page is unavailable, you can go directly to our website to choose your subscription by clicking the Buy now button. Complete the prompt instructions and make sure to use the same login credentials of your expired account.
Once done, you can check your plan details to ensure you got it right, here's what you'll need to do:
If you have to open a new QBO account, make sure to click the Buy button to get the discounted price for up to 3 months. If you purchase from the Trial account or downgrade your plan, you have to pay the regular rate.