Creators can update the reserve price of their NFT up until the point of the reserve price being met. If your reserve price has yet to be met, you will NOT be able to change the price.
How to update your reserve price:
Click on the NFTs page, and there is a drop-down menu next to the "Add Price" button
Click "Update Reserve Price"
Enter the updated reserve price.
Finalize your price by clicking "Update Price."
When clicking "Update Price", your connected wallet will prompt you to confirm the transaction by paying the gas fee required to complete the process.