In case there is an error, what help page told you this? It's just Right-Click to see the options.

Thanks for the follow-up.

While I can see the Sort option and I click on it, the bookmarks are not sorted.....

https://support.mozilla.org/en-US/kb/sort-bookmarks-quickly-find-ones-you-want#w_sorting-by-name

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address bar.

You will find Places Database near the bottom. Press the Verify Integrity button.

When done, copy and post the results here.

https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

Thanks for your quick reply. I do not have sync enabled to the best of my knowledge and I didn't see any error messages.

I followed your suggested steps and it looks like they fixed the problem. Sort now works.

Does this happen often? What causes this problem?

Here is what Verify Integrity displayed:

> Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum + Initial database size is 5120KiB + The database has been vacuumed + Final database size is 5120KiB > Task: stats + Places.sqlite size is 5120KiB + Favicons.sqlite size is 5120KiB + pragma_user_version is 54 + pragma_page_size is 32768 + pragma_cache_size is -2048 + pragma_journal_mode is wal + pragma_synchronous is 1 + History can store a maximum of 64941 unique pages + Table moz_places has 1688 records + Table moz_historyvisits has 732 records + Table moz_inputhistory has 2 records + Table moz_hosts has 0 records + Table moz_bookmarks has 1237 records + Table moz_bookmarks_deleted has 5 records + Table moz_keywords has 0 records + Table sqlite_sequence has 0 records + Table moz_anno_attributes has 2 records + Table moz_annos has 6 records + Table moz_items_annos has 0 records + Table sqlite_stat1 has 17 records + Table moz_meta has 4 records + Table moz_origins has 861 records + Index sqlite_autoindex_moz_inputhistory_1 + Index sqlite_autoindex_moz_hosts_1 + Index sqlite_autoindex_moz_bookmarks_deleted_1 + Index sqlite_autoindex_moz_keywords_1 + Index sqlite_autoindex_moz_anno_attributes_1 + Index sqlite_autoindex_moz_origins_1 + Index moz_places_url_hashindex + Index moz_places_hostindex + Index moz_places_visitcount + Index moz_places_frecencyindex + Index moz_places_lastvisitdateindex + Index moz_places_guid_uniqueindex + Index moz_historyvisits_placedateindex + Index moz_historyvisits_fromindex + Index moz_historyvisits_dateindex + Index moz_bookmarks_itemindex + Index moz_bookmarks_parentindex + Index moz_bookmarks_itemlastmodifiedindex + Index moz_bookmarks_dateaddedindex + Index moz_bookmarks_guid_uniqueindex + Index moz_keywords_placepostdata_uniqueindex + Index moz_annos_placeattributeindex + Index moz_items_annos_itemattributeindex + Index moz_places_originidindex > Task: _refreshUI

Glad to help. Safe Surfing.

The maintenance should fix issues or tell you there is a problem. As to what the problem was? I have no clue.

Thanks again!