Nginx straight-chain apk static file does not return http header content-length what's going on?

is actually a download update package for Android App. The link is a straight-chain apk file. The download progress cannot be calculated because the http header does not return content-length. Why is there no content-lenth return for a static file? Is it a problem with nginx configuration? Nginx mime configuration issues?

Mar.21,2022
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b30972-2bd1d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b30972-2bd1d.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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