What do you have selected in the Metadata area of LR. If you don't have Default, EXIF or EXIF and IPTC selected you might not see the lens info.
To see if the lens data is there open the filter menu bar by hitting the \ key then the Metadata tab/section and look under the Lens section. If the lens is listed then it is in the metadata and whatever you have selected in the Metadata area isn't showing it.
If Shootistbond007's suggestions don't help, then the most efficient way to troubleshoot this is to upload a sample problem pic to Dropbox (or similar) and post the link here. Then we can look at the pic and see which fields aren't getting imported and why.
I verified that in my LR 5.7.1, no Lens is displayed by LR for this file. However, it appears that the file has been manipulated by software other than LR, modifying to not strictly conform with the standards:
1. Exiftool issues the following warning:
[ExifTool] Warning : [minor] Adjusted MakerNotes base by 26 [ExifTool] Warning : MakerNotes pointer references previous MakerNotes directory [ExifTool] Warning : InteropIFD pointer references previous InteropIFD directory
2. The file stores many tags in both the EXIF IFD (as it should) and in the Interoperability IFD (as it shouldn't).
It's very possible that these nonconformities (especially the first one) are tripping up LR when it's trying to read the lens information. What other software has manipulated this file?
Try importing a new photo directly from the camera into LR, with no other software for downloading from the camera. Does the Lens show up in LR's Metadata panel? If not, then take a file directly from the camera's card using Mac Finder / Windows File Explorer, and upload it to Dropbox (not this forum, which sometimes in the past has modified posted images). Then post the Dropbox link.