You have an ancient drawing that requires this specific font, and you cannot find the file. Here is a recovery method using FONTALT:
If you have this font file, you can expect the following characteristics:
The Vn-uni.shx font family was created to solve the Vietnamese diacritic problem within CAD. The "Vn" stands for Vietnamese, and "uni" suggests Unicode mapping. These fonts re-map standard ASCII characters and extended characters to produce the correct combination of base letters and tone marks (dấu huyền, dấu sắc, dấu hỏi, dấu ngã, dấu nặng).
17 Nov 2025 — The standard SHX fonts folder. For Windows this is C:\Program Files\Autodesk\AutoCAD 20xx\Fonts. Install SHX fonts | SHX Fonts | AutoCAD Tips in 60 Seconds
"One or more SHX files are missing. What do you want to do ... - Autodesk