Folders not showing numbers of photos

[PeterG1]

I have recently cleared the Previews folder, as recommended, to reduce the very large folder size. Now the folders or sub-folders aren't showing the number of photos in the folder or subfolder, irrespective as to whether the folder is on the computer or a separate drive: 

[PeterG1]

Issue has resolved itself.

[F. McLion]

Would you mind sharing how it resolved itself?

[PeterG1]

I thought it had resolved itself, possibly due to time, but I have closed Lightroom and reopened it. When I reopened it the number of photos in folders didn't show up. An hour later they still don't. The numbers in Collections have always neen shown.

[F. McLion]

Can you recap what exactly(!) you did delete?

As the folders are all greyed out, I suspect the drive is off-line.

[PeterG1]

I deleted Lightroom Catalog-v13 Previews.lrdata and Lightroom Catalog-v13 Smart Previews.lrdata. The Smart Previews have rebuilt themselves. I have gone into a number of folders and the Standard Previews have been rebuilt. It effects folders on my computer and my separate hard drive. Despite the folders being greyed out both are connected and on both I have rebuilt Previews. No photos are shown as missing.

[Jim Wilde]

Close LrC, then delete (or rename) the Lightroom Catalog-v13 Helper.lrdata folder. Then restart LrC. Does that help?

[PeterG1]

They started showing again, but this time when I closed Lightroom and reopened they showed OK. I hadn't seen the message from Jim Wilde so hadn't tried that!

[GoldingD]

I assume that a Passport hard drive is an external hard drive, probably USB. Was it disconnected, in power save, or off when you had the issue?

Yes, I do not see a ? mark in the first screenshot Folders panel indicating a folder issue, but still??

[PeterG1]

The Passport hard drive is a 4TB hard drive which was connected all the time. The issue was the same for folders held on the PC (not on the separate hard drive).