Greetings MonicaS718,
Based on the description you've provided, let's try testing a different memory card with the camera. It may be to where the memory card is beginning to malfunction to where it's having trouble with writing data to it. The reason why the images show up on the camera's LCD and may have trouble with transferring is due to the image we see on the camera being a thumbnail of the actual file itself and not the actual image.
Let's format the new card inside the camera prior to using it to ensure the card is initialized for use on your PowerShot SX740 HS camera. Please note that formatting a card will erase all data from the card. If the camera is able to transfer all pictures taken with it then one option on the old card is to back up as many photos as possible on to your computer. Then format the old card and then test to see if the issue is resolved.
If using a new memory card produces the same results then the next step is to suggest to send the camera in to our facility since it may be an issue with how the camera is writing photos to the memory card when a picture is taken.
Canon U.S.A., Inc. has created a new online repair portal that allows you to set up service in a few simple steps. The repair portal gives you the ability to set up service for multiple pieces of equipment at once, and to receive a repair estimate in the majority of cases, depending on your model and issue. The portal also allows you to upload images or videos that will assist us in repairing your product. You can also select how you wish to be notified of the progress of your repair. The portal's service history section allows you to view all services that have been performed on any of your camera or video products since January 7, 2020.
Please follow the link below to access our online repair portal to arrange for service:
https://mycanon.usa.canon.com/signin
Instructions for Accessing and Using the Online Repair Portal.
You will need to access or create your My Canon Account.
If you already have a My Canon Account and your product is already registered, simply click on the “Get Repair Services” link on the left menu and follow the onscreen instructions to arrange for service for your product.
If you have a My Canon Account and your product is not registered, you must register your product first. Click on the “Get Repair Services” link on the left menu, then click on the “Register Product” link on the right. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.
If you do not have a My Canon Account, you will need to create one. After you create your account, click on the “Add Product” link to register your first product. After your product is registered, click on the “Get Repair Service” link on the left menu and follow the onscreen instructions to arrange for service for your product.
Once you have completed the repair request, you will have an opportunity to print a copy of the request for your records. This request form will also contain shipping instructions and an address label that you will attach to the outside of your shipping box when mailing your equipment for repair.
