Hello, I'd want to separate this scenario into two cases based on your explanation. The first is that neither the SD card nor the programs that are loaded on it are invisible on your Android device. Facing this, the only fix is to check the connection. The second one is that your Android phone is seeing the SD card rather than the apps. Fixing this case, giving the SD card an Android-compatible file system, or performing data recovery is worth a shot.
Case 1: Android phone sees no SD card and the apps installed
If you encounter the SD card not showing on the phone trouble, you're recommended to check the connection between the SD card and your phone. You can try a new SD card adapter or SD card reader to connect the storage device and your phone.
Or, you can insert the SD card into a computer to see if it shows up there. If it does, then the trouble is fixed. If it doesn't, the related articles are presented for your reference:
SD Card Not Showing up in Windows, Fixes & Causes
How to Fix SD Card not Showing up, Reading or Recognizing on Mac?
Case 2: Android phone sees SD card but not the apps installed
If the Android is able to see your SD card but fails to see the downloaded applications on it, you should take data loss or file system incompatibility into consideration.
Solution 1: Perform data recovery work with iBoysoft Data Recovery
If you deleted the applications on the SD card accidentally or lost them previously, you should recover them ASAP! iBoysoft Data Recovery is highly recommended because it is able to recover your deleted or lost files before you rewrite files to your SD card.
With an intuitive interface, you can recover the missing applications on it with 5 easy steps:
Step 1: Free download and install iBoysoft Data Recovery Software on your computer.
Step 2: Insert your SD card into your computer and launch the recovery software.
Step 3: Select the Data Recovery mode in the main interface and select your SD card in the device list.
Step 4: Click Next to start disk scanning and click Preview to check the scanning results.
Step 5: Click Recover to save the recovery results to another drive or volume to avoid further data loss.
Solution 2: Format the SD card on your computer
Sometimes, the SD card files not showing up issue happens due to file system incompatibility. Mobile phone is able to recognize FAT32, Ext3, and Ext4 file system formats. If your SD card is formatted as non-FAT32, non-Ext3, or Ext4, then it's likely not showing up on your phone. You can format your SD card on Windows to give it a phone-compatible file system.
Before formatting your SD card, make sure you have made a full backup of all files and documents on it. Formatting will wipe out all the things on a hard drive.
Step 1: Double-click 'My Computer' (or 'This Computer') on the desktop to open it.
Step 2: Select your SD card shown on the panel and right-click it.
Step 3: Click the Format... option, and then a Format panel will pop up.
Step 4: Select FAT32 in the file system box, and click Start. Then, wait for your SD card to be formatted.
Hope this answer help you! Good luck!