Apple 12 HEIC Files Will Not Import into LR Classic

[Jim_Moyer]

I have a new iPhone 12 Pro Max.  I have an up-to-date LR Classic on a Mac Air.

I am shooting HEIC files on the iPhone.  They frequently will not import into Lightroom Classic.  When the import problem happens, LR says it is importing the files but there is no preview in LR; I just see a gray box and a "!" symbol.  When the HEIC files do import, after editing in LR I cannot export a jpg from LR to my Mac Air desktop for sharing online.  I get an error box in LR which says the file may be damaged.

So, (a) sometimes LR Classic will not import from iPhone 12; and (b) sometimes LR Classic will not export a jpg to hard drive with a file from the iPhone 12.

Thank you for any assistance you can provide!  I love the iPhone 12 as a supplement to my Nikon camera, but I have to get the files into my LR catalog, which is where all my photo work resides.

Jim

[Jim_Moyer]

ps

I am using Lightroom Classic 10.11 and MacOS Catalina 10.15.6

-and-

The iPhone 12 Pro Max is two weeks old.