Why is my image specified by img src not shown on my webpage?

[weitse-hsu]

I'm setting up pages on my personal website(hugo academics) and here is the structure of one of the folders I have:

.
├── ABF.md
├── EXE.md
├── Figures
│   ├── sampling.gif
│   └── sampling_compressed.gif
├── HREMD.md
├── MetaD.md
├── REUS.md
├── TREMD.md
├── US.md
├── _index.md
├── alchemical_MetaD.md
├── appendix.md
├── intro.md
└── test.gif

In _index.md, I have the following lines to read in a GIF file:

<center>
<img src="Figures/sampling_compressed.gif">
</center>

In intro.md, which is in the same folder as _index.md, I also have the same lines to read in the same GIF file. However, in localhost, the GIF file is shown in the page made by _index.md, but not the one built by intro.md. How can I solve the problem and why is this happening? Thanks in advance!