Effects quit working on Acoustic AG30 amp. what are the likely problems and costs to repair?

You might have a shorted rectifier or capacitor in the power supply circuit. Check that first.

Relay?? I've never seen a guitar or bass amp with "speaker protection relays"...usually they're either on or off. Check the simple stuff 1st...is speaker cable from head to cabinet and/or the input cable from bass to the amp good? Check the "Direct Out" for a line level signal (must be connected to a PA or other amplifier) as this is your preamp out signal. Also, plug a shielded cable from "Effects Send" to "Effects Return"...this will verify "effects" loop issues if any. Lastly, vibration test...use a clenched fist across the top, sides and bottom of wood cabinet to lightly "jar" the internal circuits. If it starts working even for an instant, I would suspect intermittent connection inside.

On some amps there needs to be a footswitch inserted in the control jack to activate the effects circuit. Contact Crate to see if that's the case with your amp.
http://www.crateamps.com/support/index.php

My A2 effect not work properly

NEVER CONNECT PEDALS THROUGH THE EFFECT LOOP OF AN AMP. They are NOT design to work at the same signal levels !!! ONLY use effect units that are design to be used in amp effects in the amp effects loop/

Most of the pedals are daisy chained right from the guitar. The output of the daisy chain goes into the DI box set to ground lift. An XLR to XLR cable goes from the DI box to the amp or mixer. Do NOT try to loop the sends and receives of the amp through PEDALS! The sends and receives are LINE LEVEL which is too high for pedals. The sends and receives are for external effects MODULES and EQ's that take line level. Some of those effect units have a foot switch to turn them on and off.

You should be using XLR to XLR cable, NOT a 1/4 inch cable. There is a problem of the 1/4 inch being the unbalanced version and is not compatible with this unit's input.

Use the XLR to XLR mic cable and it will work fine.

The cable you have would work for one of those cheap Karaoke machines...

BURNT OUT FUSE.

Ok, so I hope you realize the Fender FM25DSP guitar amplifier is an "entry level" NON-valve amp with a DSP chip that has model shaping tones. I am sorry but this is a toy and Fender did not spend the tens of thousands of US dollars to have built-in tones that truly 'kill". This not digital modelling like Line 6 or Fractal Audio did and so you have a problem from the start. This amp was always intended as an entry level amp for the bedroom only and never to be used on stage.
Jazz and acoustic modes have some similarities requiring mid-range boost and some rounding. Not easy to achieve with a DSP chip that costs about US$10 to manufacture. Sorry, consider using the amp for practice but look at a more serious valve amps for live on stage