https://www.gamespot.com/articles/no-mans-sky-save-bug-addressed-in-new-pc-update-ps/1100-6460759/

Hello Games has deployed another hotfix for No Man's Sky. This latest patch is currently available on PC (with other platforms following soon) and addresses a number of other bugs that have cropped up in the wake of the big Next update, most notably an issue that would apparently wipe players' save data.

Following the Next update, many players have discovered that their save data would display their playtime correctly but load from the beginning of the game, apparently erasing their data. PC players have figured out their own workaround to this issue and detailed it on Reddit, but the new 1.51 patch should resolve the issue for all players.