Hi,
Please check if you saved the changes after adding the tag(s). Sharing the steps to save tags to a file below, for your reference.
1. Select a file to open the right panel
2. Scroll down to the 'Tags' field on the right panel
3. Type in the tag you want to add to that file. Press 'Enter'.
4. If you want to add more tags, you can enter them one by one by repeating step 3.
5. Finally Save all the tags you have entered against the file by clicking on the Blue Tick (shown below)
Please get back, if you are still facing some issue.