For Steam DayZ Launcher.

Step 1. Open DayZ Launcher.

Step 2. Click on the Mods option under Parameters. On the left hand side.

Step 3. Find the mod that is requiring verification.

Step 4. Click the arrow to the far right of said mod.

Step 5. Click the 3 dots you see under the mods picture.

Step 6. Click Repair on the drop down that appeared.

For DZSA Launcher.

Step 1. Open DZSA Launcher.

Step 2. Click Mods in the top left corner, next to Servers.

Step 3. Find the mod requiring verification.

Step 4. Click the circle arrows next to the updated time.

TIP. It is recommended that you close either launcher after verifying the mod.