From memory, the rain gauge is now about 2 years old and, today, the reed switch failed :( . Fortunately, it's quite easy to repair by soldering in a new switch:

The replacement part is a Cynergy3 TRA291G/20-30

... And there's a couple of things to watch out for:

• The component has flat legs and can be positioned in 2 ways, so check by closely examining the reed, checking that the magnet will actually close the contact when it swivels past.
• As standard, the reed is positioned on the underside of the board, but positioning on the topside, as shown above, ensures it gets activated by the magnet more readily.